Optical disk and method and apparatus for recording and then playing information back from that disk

ABSTRACT

An optical disk having a diameter less than 140 mm and, a thickness of 1.2 mm±0.1 mm, with a plurality of record tracks having data recorded thereon as embossed pits representing information and exhibiting a track pitch in the range between 0.646 μm and 1.05 μm; with the tracks being divided into a lead-in area, a program area and a lead-out area. The data includes table of contents (TOC) information recorded in a plurality of sectors in at least one TOC track and user information recorded in a plurality of sectors in user tracks; with the TOC information including addresses of start sectors recorded in the user tracks. The data (both user and TOC information) is encoded in a long distance error correction code having at least eight parity symbols, and is run length limited (RLL) modulated.

This application is a division of application Ser. No. 08/405,852, filedMar. 13, 1995 Mar. 17, 1995 now U.S. Pat. No. 5,715,355.

BACKGROUND OF THE INVENTION

The invention relates to a novel optical disk and, more particularly, tothat disk, to a method of recording and reading information on the diskand to apparatus for carrying out that method.

Optical disks have been used as mass storage devices for computerapplications, and such optical disks are known as CD-ROMs. The diskwhich is used as the CD-ROM is modeled after the standard compact disk(CD) that has been developed for audio applications and is basically anaudio CD with various improvements and refinements particularly adaptedfor computer applications. Using such a CD as a standard. the CD-ROM hasa data storage capacity of about 600 Mbytes. By using audio CDtechnology as its basis, the, CD-ROM and its disk drive have becomerelatively inexpensive and are quite popular.

However, since conventional audio CDs with their inherent format andstorage capacity have been adapted for CD-ROMS, it has heretofore beendifficult to improve the data storage capacity. In typical computerapplications, a capacity of 600 Mbytes has been found to beinsufficient.

Also, the data transfer rate that can be obtained from audio CDsgenerally is less than 1.4 Mbits/sec (Mbps). However, computerapplications generally require a transfer rate far in excess of 1.4Mbps; but it is difficult to attain a faster transfer rate withconventional CD-ROMS.

Yet another disadvantage associated with conventional CD-ROMs, and whichis due to the fact that the audio CD format has been adapted forcomputer applications, is the relatively long access time associatedwith accessing a particular location on the disk. Typically, relativelylong strings of data are read from audio CDs, whereas computerapplications often require accessing an arbitrary location to read arelatively small amount of data therefrom. For example, accessing aparticular sector may take too much time for the CD controller toidentify which sector is being read by the optical pick-up.

A still further difficulty associated with CD-ROMs, and which also isattributed to the fact that such CD-ROMs are based upon audio CDtechnology, is the error correcting ability thereof. When audio data isreproduced from an audio CD, errors that cannot be correctednevertheless can be concealed by using interpolation based upon the highcorrelation of the audio information that is played back. However, incomputer applications, interpolation often cannot be used to concealerrors because of the low correlation of such data. Hence, the data thatis recorded on a CD-ROM must be encoded and modulated in a formexhibiting high error correcting ability. Heretofore, data has beenrecorded on a CD-ROM in a conventional cross interleave Reed-Solomoncode (CIRC) plus a so-called block completion error correction code.However, the block completion code generally takes a relatively longamount of time to decode the data, and more importantly, its errorcorrection ability is believed to be insufficient in the event thatmultiple errors are present in a block. Since two error correction code(ECC) techniques are used for a CD-ROM, whereas only one ECC techniqueis used for an audio CD (namely, the CIRC technique), a greater amountof non-data information must be recorded on the CD-ROM to effect sucherror correction, and this non-data information is referred to as“redundant” data. In an attempt to improve the error correction abilityof a CD-ROM, the amount of redundancy that must be recorded issubstantially increased.

OBJECTS OF THE INVENTION

Therefor, it is an object of the present invention to provide animproved optical disk having particular use as a CD-ROM which overcomesthe aforenoted difficulties and disadvantages associated with CD-ROMswhich have been used heretofore.

Another object of this invention is to provide an optical disk whichexhibits a higher access speed, thereby permitting quick access ofarbitrary locations, such as sectors, to be accessed quickly.

A further object of this invention is to provide an improved opticaldisk having a higher transfer rate than the transfer rate associatedwith CD-ROMs heretofore used.

A further object of this invention is to improve the storage capacity ofan optical disk, thereby making it more advantageous for use as aCD-ROM.

An additional object is to provide an improved optical disk which storesdata with reduced redundancy.

Still another object of this invention is to provide an improvedrecording format for an optical disk which enhances the error correctingability thereof.

Another object of this invention is to provide an optical disk having asubstantially improved recording density, thereby facilitating use ofthe disk as a CD-ROM.

A further object of this invention is to provide an improved opticaldisk having data recorded in sectors, with each sector having a sectorheader that is easily and rapidly read, particularly because the sectorheader is not encoded in a form which requires a substantially longamount of time before it is successfully decoded and recognized.

Various other objects, advantageous and features of the presentinvention will become readily apparent from the ensuing detaileddescription, and the novel features will be particularly pointed out inthe appended claims.

SUMMARY OF THE INVENTION

In accordance with this invention, an optical disk, a method andapparatus for recording that disk and a method and apparatus for readingdata from that disk are provided. The disk has a diameter of less than140 mm, a thickness of 1.2 mm±0.1 mm, and a plurality of record tracksexhibiting a track pitch in the range between 0.646 μm and 1.05 μm withdata recorded in those tracks as embossed pits. The tracks are dividedinto a lead-in area, a program area and a lead-out are, with table ofcontent (TOC) information being recorded in at least one TOC track inthe lead-in area and user information recorded in a plurality of usertracks in the program area. Each track is divided into sectors and theTOC information includes addresses of the start sectors of each usertrack. The data (both TOC and user information) is encoded in a longdistance error correction code having at least eight parity symbols, theencoded data being modulated and recorded on the disk. Preferably, thedata is modulated as run length limited (RLL) data.

In the preferred embodiment, the data is recorded with a linear densityin the range between 0.237 μm per bit and 0.378 μm per bit. Also, theprogram area is disposed in a portion of the disk having a radius from20 mm to 65 mm.

The format of the data advantageously permits rapid access to a desiredsector. Reduced redundancy in the recorded data and a higher storagecapacity are attained. Advantageously, the optical disk may record datahaving particular computer application, referred to computer data orvideo and audio data, the latter being compressed by the so-called MPEG(Moving Picture Image Coding Experts Group) technique. Audio data whichalso may be recorded preferably is compressed and then multiplexed withthe MPEG-compressed video data.

The error correction code used with the present invention preferably isa long distance code having at least eight parity symbols. ECCtechniques which have been used heretofore have relied upon so-calledshort distance codes in which a block of data is divided into twosub-blocks, each sub-block being associated with a number of paritysymbols, such as 4 parity symbols. It is known, however, that 4 paritysymbols may be used to correct 4 data symbols, and if 4 data symbols ineach sub-block are erroneous, the total number of 8 erroneous datasymbols can be corrected. But, if one sub-block contains 5 erroneousdata symbols, whereas the other sub-block contains 3 erroneous datasymbols, use of the short distance code may be effective to correct only4 data symbols in the one sub-block, thus permitting a total errorcorrection of 7 data symbols. But, in the long distance code, the blockof data is not sub-divided; and as a result, all 8 erroneous datasymbols, if present in the long distance coded data, can be corrected.

As another feature of this invention, the RLL code that is usedpreferably converts 8 bits of input data into 16 bits of data forrecording (referred to as 16 channel bits) with no margin bits providedbetween successive 16-bit symbols. In RLL codes used heretofore, 8 databits are converted into 14 channel bits and three margin bits areinserted between successive 14-bit symbols. Thus, the present inventionachieves a reduction in redundancy.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description, given by way of example and notintended to limit the present invention solely thereto, will bestunderstood in conjunction with the accompanying drawings in which:

FIG. 1 is a block diagram of the preferred technique by which opticaldisks are made in accordance with the present invention;

FIG. 2 is a block diagram of apparatus incorporated in the presentinvention for reproducing data from the optical disk that has been madein accordance with the technique shown in FIG. 1;

FIG. 3 is a schematic representation of the recording areas for the diskmade by the technique shown in FIG. 1;

FIG. 4 is a schematic representation showing the recording areas of FIG.3 in greater detail;

FIG. 5 is a schematic representation of another format of the recordingareas;

FIG. 6 is a schematic representation of still another format of therecording areas;

FIG. 7 is a schematic representation of yet another format of therecording areas;

FIG. 8 is a tabular representation of a portion of the informationrecorded in the TOC region of the disk;

FIG. 9 is a tabular representation of another portion of the datarecorded in the TOC region;

FIG. 10 is a schematic representation of a sector of data recorded onthe disk;

FIGS. 11A–11E are tabular representations of different types of subcodedata that may be recorded in a sector;

FIG. 12 is a tabular representation of copyright data that may berecorded as subcode information in a sector;

FIG. 13 is a tabular representation of application ID information thatmay be recorded as the subcode information in a sector;

FIG. 14 is a tabular representation of time-code data that may berecorded as the subcode information in a sector;

FIG. 15 is a tabular representation of picture-type data that may berecorded as the subcode information in a sector;

FIG. 16 is a tabular representation of ECC type data that may beincluded in the TOC information recorded in the TOC regions;

FIG. 17 is a schematic representation of one frame of error correctionencoded data, identified as a C1 code word;

FIG. 18 is a schematic representation of the long distance errorcorrection code format used with the present invention;

FIG. 19 is a schematic representation of a short distance errorcorrection code format that could be used with the present invention;

FIG. 20 is a schematic representation of the sequential order ofrearranged data symbols after those symbols have been played back fromthe disk;

FIG. 21 is a schematic representation of a sector of data that has beenerror correction encoded;

FIG. 22 is a schematic representation of a block code of errorcorrection encoded data in the long distance format;

FIG. 23 is a schematic representation of a block code of errorcorrection encoded data in the short distance format;

FIG. 24 is a schematic representation of a string of data symbolsexhibiting EFM modulation;

FIG. 25 is a flowchart explaining how margin bits are selected in theEFM modulated data shown in FIG. 24;

FIG. 26 is a block diagram of an EFM modulator that can be used toproduce the data string shown in FIG. 24;

FIG. 27 is a schematic representation of a frame of EFM modulated data;

FIG. 28 is a table which explains how margin bits are selected/inhibitedwhen forming the string of EFM data shown in FIG. 24;

FIGS. 29A–29D are explanatory waveforms which are useful inunderstanding how margin bits are selected;

FIG. 30 is a block diagram of a modulator that may be used with thepresent invention;

FIG. 31 is a block diagram of a demodulator that may be used with thepresent invention;

FIG. 32 is a block diagram of apparatus which may be used to supply datafor the recording technique shown in FIG. 1; and

FIG. 33 is a block diagram of data recovery apparatus that may be usedwith the playback apparatus shown in FIG. 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention records different types of data on an opticaldisk, preferably for use as a CD-ROM but also adapted for use as adigital video disk (DVD). Such data may be file data or application datato be used by a computer, or it may comprise video data which sometimesis referred to herein as motion picture data which includes imageinformation and audio information and which preferably is compressed inaccordance with the various conventional video data compressionstandards, such as those known MPEG-1, MPEG-2, or when still videopictures are recorded, JPEG. It will be appreciated, therefore, that theinformation on the disk admits of “multimedia” applications.

Before describing the technique used to record data on the optical disk,a brief description is provided of the disk itself. The physicalparameters of the optical disk used with the present invention are quitesimilar to the conventional audio CD; and for this reason, a drawingfigure of the disk is not provided. Nevertheless, it will be appreciatedthat the diameter of the disk is 140 mm or less, preferably 120 mm or135 mm. Data is recorded in tracks, and will be described in greaterdetail, having a track pitch in the range between 0.646 μm and 1.05 μm,and preferably in the range of 0.7 to 0.9 μm. Like audio CD data, thedata recorded on the optical disk is in the form of embossed pits havinga linear density in the range between 0.237 μm per bit and 0.387 μm perbit, although this range could be in the range of 0.3 μm to 0.4 μm perbit. Data is recorded in that portion of the disk having a radius from20 mm to 65 mm. The disk, whose thickness is 1.2 mm±0.1 mm, is intendedto be driven for a playback operation such that its linear velocity isin the range of 3.3 m to 5.3 m per second.

As a result of the linear density and track pitch of the disk,information is optically read from the disk by a pick-up head whichprojects a light beam of wavelength λ through a lens having a numericalaperture NA such that the projected beam exhibits a spatial frequency l,where l=λ/(2NA). The light source for the optical pick-up preferably isa laser beam whose wave length is λ=635 nm, this laser beam beingprojected through a lens whose numerical aperture is NA=0.52, resultingin the spatial frequency l=611 nm.

Typical examples of the physical parameters associated with the opticaldisk are as following:

-   -   Disk diameter=120 mm.    -   Program area=23 mm to 58 mm.    -   Track pitch=0.84 μm.    -   Linear density=0.307 μm.        This results in a data storage capacity of 4.4 Gbytes.

One proposed structure for recording data on the optical disk is knownas the EFM Plus frame (EFM refers to eight-to-fourteen modulation). AnEFM Plus frame is formed of 85 data symbols (each symbols is a 16-bitrepresentation of an 8-bit byte) plus two synchronizing symbols thusconsisting of 87 16-bit symbols. One sector is comprised of 14×2 EFMplus frames. But, the amount of user information that is present in asector, that is, the amount of information which contains useful dataand thus excludes sector header information, error detection code (EPC)information, et cetera, is 2048 symbols. Accordingly, the efficiency ofthe EFM Plus format may be calculated as:(2048×16)/(87×16×14×2)=0.8407.That is, the efficiency of the EFM Pius format is approximately 84%,which means that 84% of all of the data that is recorded in a sector isuseful data. Therefore, if the storage capacity of the optical disk is4.4 Gbytes, as mentioned above, the amount of user data that can bestored on the disk is 84%×4.4 Gbytes=3.7 Gbytes.

Of course, if the track pitch is varied and/or if the linear density ofthe embossed pits is varied, the storage capacity of the disk likewiseis varied. For example, if the track pitch is on the order of about0.646 μm, the storage capacity of the disk may be on the order of about6.8 Gbytes, whereas if the track pitch is on the order of about 1.05 μm,the storage capacity is on the order of about 4.2 Gbytes. As a practicalmatter, however, the spatial frequency of the pick-up beam determinesthe minimum track pitch and minimum linear density because it isdesirable that the track pitch be no less than the spatial frequency ofthe pick-up beam and the linear density be no less than one-half thespatial frequency of the pick-up beam.

When compared to the audio CD, the linear density of the recorded dataof the optical disk used in the present invention is approximately 1.7times the linear density of the audio CD and the recording capacity ofthe optical disk used with the present invention is approximately 5.5times the recording capacity of the audio CD. The optical disk of thepresent invention is driven to exhibit a linear velocity ofapproximately four times the linear velocity of the audio CD and thedata transfer rate of the optical disk of the present invention isapproximately 9 Mbps, which is about six times the data transfer rate ofthe audio CD.

With the foregoing in mind, reference is made to FIG. 1 which is a blockdiagram of the technique used to make an optical disk of the type thathas just been described. An input terminal 121 is supplied with userdata to be recorded, this data being formed of, for example, multiplexedvideo and audio information, title data and sub-information such as, butnot limited to, computer files, character data, graphic information, etcetera. The data supplied to input terminal 121 is produced by theapparatus shown in FIG. 32 and will be described below.

The user data is coupled to a change-over switch 124 which also isadapted to receive table of content (TOC) information supplied to theswitch from an input terminal 122 via a TOC encoder 125. The TOCinformation identifies various parameters of the disk which are used foraccurate reproduction of the user information recorded thereon; and theTOC information also includes data related to the user information perse, such as information that is helpful in rapidly accessing the userinformation recorded in particular tracks. The structure of the TOCinformation is described below.

Switch 124 selectively couples user data supplied at input terminal 121and encoded TOC data supplied at input terminal 122 to an or detectioncode (EDC) adder 127. As will be described, TOC information is recordedon one portion of the disk and user data is recorded on another portion;and switch 124 selects either the TOC information or the user data atthe appropriate times. As will be described below in conjunction with,for example, FIG. 21, the error detection code is added at the end of asector of user data or TOC information; and adder 127 serves to producethe error detection code after a sector of data has been received andthen adds the error detection code to the end of the sector of data. Inthe preferred embodiment, a sector is comprised of 2048 bits of usefuldata plus parity bytes, plus sector header data, plus a number of“reserved” bytes, plus the EDC code.

A sector header adder 128 is adapted to add a sector header to eachsector of user information supplied thereto by way of EDC adder 127. Aswill be described below in conjunction with FIG. 10, a sector headerincludes a synchronizing pattern and information useful to rapidlyidentify access the sector. Such information, particularly in sectorscontaining user data, includes subcode information which is coupled tothe sector header adder by way of a sector header encoder 129, thelatter operating to encode subcode information supplied thereto by wayof input terminal 123. Such subcode information is generated by asuitable source and, as will be described further below in conjunctionwith FIG. 11, it is used to provide helpful identifying and controlinformation related to the user data that is recorded on the disk. Forexample, the subcode information identifies the track number in whichthe sector which contains this subcode information is recorded,copyright management information which determines whether the datareproduced from the disk, such as video data, may be copied, applicationID information which designates the particular user-application for thedata recorded in the sector, time code data which represents timeinformation at which the user data is recorded, and information relatingto video pictures that may be recorded on the disk, such as thedistance, or separation, between a video picture recorded in this sectorand the next-following and the next-preceding video pictures. A systemcontroller 110 controls sector header encoder 129 to make certain thatthe proper subcode information and other sector header information (asshown in FIG. 10) is placed in the proper data location for properrecording in a user track.

User data, including the sector header added thereto by reason of sectorheader adder 128, is subjected to error correction encoding carried outby an ECC circuit 132 in combination with a memory 131 and a memorycontrol section 133, the latter being controlled by system controller110. An example of ECC encoding that may be used with the presentinvention, subject to modification so as to be applicable to the datarecorded on the optical data is described in U.S. Pat. No. Re. 31,666.In one embodiment of the present invention, the ECC encoding produced bycircuit 132 is convolution coding and is described in greater detailbelow in conjunction with FIG. 17. It is sufficient for an understandingof FIG. 1 simply to point out that the ECC encoding assembles a frame ofdata bytes or symbols, referred to as a C2 code word formed of, forexample, 116 bytes or symbols, and generates C2 parity bytes as afunction of a respective data byte or symbol in a predetermined numberof C2 code wards. For examples if the data bytes or symbols in each C2code word exhibit the sequence 1, 2, . . . 116, a C2 parity byte, orsymbol, may be produced by combining byte 1 from C2 code word C2₁ andbyte 2 from C2₂. Another C2 parity byte may be produced by combining thethird byte of C2 code word C2₃ and the fourth byte of C2₄. In thismanner, the C2 parity bytes are generated by a cross-interleavetechnique; and as an example, 12 such C2 parity bytes are added to theC2 code word C2₁, even though such C2 parity bytes relate to data bytesincluded in other C2 words. Then, C1 parity bytes are generated for theC2 word (such as C2₁) to which has been added the C2 parity bytes,resulting in what is referred herein as a C1 code word (such as C1₁).The resultant C1 code word, consisting of 116 data bytes, plus 12 C2parity bytes, plus 8 C1 parity bytes is stored in memory 131.

The sequential order of the data bytes in the C1 code words stored inmemory 131 is rearranged by, for example, delaying the odd bytes so asto form an odd group of data bytes and an even group of data bytes.Since each group consists of only one-half of the data bytes included inthe C1 code word, an odd group of data bytes of one C1 code word iscombined with an even group of data bytes of the next-following C1 codeword, thus forming a disarranged order of bytes. This disarranged orderimproves the burst error immunity of the ECC encoded data. Thedisarranged order of the ECC-encoded bytes is supplied from memory 131to a modulator 140 which, preferably, carries out 8-to-16 modulation,although 8-to-14 (EFM) modulation could be used, if desired.

Memory controller 133 supplies to memory 131 the necessary read andwrite addresses to enable the generation of the C2 parity bytes incross-interleaved form and also to rearrange the sequential order of thedata bytes into the aforementioned disarranged order.

In the preferred embodiment of the ECC encoding technique, a longdistance code, also known as the L format, is use. The L format resultsin C1 code words that are arranged as shown in FIG. 18, describedfurther below. If desired, the ECC-encoded data may exhibit a shortdistance code or S format, such as is depicted in FIG. 19, describedbelow. Depending upon whether the L format or the S format is selected,system controller 110 controls memory controller 113 such that the readand write operations of memory 131 permit the data bytes to be ECCencoded in either the L format or the S format.

Modulator 140 serves to converts 8-bit bytes supplied thereto frommemory 131 into 16-bit symbols. Each symbol is run length limited (RLL),as will be described. It will be appreciated that, by generating 16-bitsymbols, the accumulated digital sum value (DSV), which is a function ofthe run length of the digital signal, that is, the number of consecutive0s or the number of consecutive 1s, is limited to permit the DCcomponent which is produced as a function of such consecutive 0s or 1s,to remain at or close to 0. By suppressing the DC, or lower frequencycomponent of the digital signal that is recorded, errors that otherwisewould be present when that digital signal is reproduced are minimized.

Modulator 140 thus produces a recording signal which is coupled tocutting apparatus 150. This apparatus is used to make an original diskfrom which one or more mother disks may be produced and from whichcopies may be stamped for distribution to end users. That is, suchstamped disks constitute the CD ROMs.

In one embodiment, the cutting apparatus includes an electro-opticalmodulator 151 which relies upon the so-called Pockels effect to modulatea light beam that is used to “cut” an original disk. This original diskis used by a mastering apparatus 160 to produce a master of the originaldisk. The mastering apparatus relies upon conventional techniques, suchas development and vacuum deposition, to produce a plurality of motherdisks. Such mother disks are used in stompers which ejection mold copiesthat subsequently are packaged and distributed. Blocks 171 and 172 inFIG. 1 are intended to represent the injection molding and packagingapparatus in manufacturing such disks. The completed disk is depicted asdisk 100.

The technique used to reproduce the information recorded on optical disk100 now will be described in conjunction with the block diagram shown inFIG. 2. Here, the disk is optically read by an optical pickup 212 whichprojects a light beam, such as a laser beam having the spatial frequencyl=λ/2na, this beam being reflected from the disk and detected by aconventional pickup detector. The detector converts the reflected lightbeam to a corresponding electrical signal which is supplied from pickup212 to a waveform equalizer 213 and thence to a phase locked loop clockreproducing circuit 214 and to a demodulator 215. Transitions in therecovered electrical signal are used to synchronize the phase lockedloop to extract therefrom the clock signal which was used to record dataon the disk. The extracted clock is coupled to demodulator 215 whichperforms RLL demodulation that is described in greater detail below inconjunction with FIG. 31. Suffice it to say that if data is recorded ondisk 100 as 16-bit symbols, demodulator 215 demodulates each 16-bitsymbol to an 8-bit symbol or a byte.

The demodulated data reproduced from disk 100 is supplied to a ringbuffer 217. The dock signal extracted by phase locked loop clockreproducing circuit 214 also is supplied to the ring buffer to permitthe “clocking in” of the demodulated to data. The demodulated data alsois supplied from demodulator 215 to a sector header detector 221 whichfunctions to detect and separate the sector header from the demodulateddata.

Ring buffer 217 is coupled to an error correcting circuit 216 whichfunctions to correct errors that may be present in the data stored inthe ring buffer. For example, when data is recorded in the long distancecode formed of, for example, C1 code words, each comprised of 136symbols including 116 symbols representing data (i.e. C2 data), 12symbols representing C2 parity and 8 symbols representing C1 parity,error correcting circuit 216 first uses the C1 parity symbols to correcterrors that may be present in the C1 word. A corrected C1 word isrewritten into ring buffer 217; and then the error correcting circuituses the C2 parity symbols for further error correction. Those datasymbols which are subjected to further error correction are rewritteninto the ring buffer as corrected data. Reference is made toaforementioned U.S. Pat. No. RE 31,666 for an example of errorcorrection.

In the event that an error in the sector header is sensed, errorcorrecting circuit 216 uses the C1 parity symbols to correct the sectorheader, and the corrected sector header is rewritten into a sectorheader detector 221. Advantageously, the C2 parity symbols need not beused for sector header error correction.

As mentioned above, the input data symbols supplied four errorcorrection encoding exhibit a given sequence, but the error correctionencoded symbols are rearranged in a different sequence for recording. Inone arrangement, the odd and even symbols are separated and the oddsymbols of a C1 code word are recorded in an odd group while the evensymbols of that C1 code word are recorded in an even group.Alternatively, odd and even symbols of different C1 code words may begrouped together for recording. Still further, other sequentialarrangements may be used to record the data. During playback, errorcorrecting circuit 216 and ring buffer 217 cooperate to return therecovered data symbols to their original, given sequence. That is, thedata symbols may be thought of as being recorded in a disarranged orderand the combination of the error correcting circuit and ring bufferoperate to rearrange the order of the symbols in a C1 code word to itsproperly arranged sequence.

Error corrected data stored in ring buffer 217 is coupled to errordetecting circuit 222 which uses the EDC bits added to the recorded databy EDC adder 127 (FIG. 1) to detect an uncorrectable error. In the eventthat data cannot be corrected, EDC detector 222 provides a suitableindication, such as an error flag in a particular uncorrectable byte oran error flag in an uncorrectable C1 code word, and the error correcteddata, either with or without such error flags, as the case may be, iscoupled to output terminal 224.

In addition, TOC information that is recovered from disk 100, afterbeing error corrected by error correcting circuit 216 and error detectedby EDC detector 222, is coupled to a TOC memory 223 for use incontrolling a data playback operation and for permitting rapid access touser data. The TOC information stored in memory 223, as well as sectorinformation separated from the reproduced data by sector header detector221 are coupled to a system controller 230. The system controllerresponds to user-generated instructions supplied thereto by a userinterface 231 to control disk drive 225 so as to access desired tracksand desired sectors in those tracks, thereby reproducing user datarequested by the user. For example, the TOC information stored in TOCmemory 223 may include data representing the location of the beginningof each track; and system controller 230 responds to a user-generatedrequest to access a particular track to control disk drive 225 such thatthe requested track is located and accessed. Particular identifyinginformation representing the data in the accessed track may be recoveredand supplied to system controller 230 by sector header detector 221 sothat rapid access to such data may be achieved. A further description ofthe TOC information and sector information useful for controlling thedisk drive in the manner broadly mentioned above is discussed in greaterdetail below.

It will be appreciated from the ensuing discussion of FIGS. 10 and 21that sector header information that is recovered from the disk may beerror corrected by using the C1 parity symbols included in the same C1code word as the sector header. There is a high probability that anyerrors that may be present in the sector header can be corrected byusing the C1 parity symbols only. Since a C1 code word contains C2parity symbols that are generated from the data symbols included indifferent C1 code words, sector information is quickly detected quicklyby not waiting for all of the C2 parity symbols to be assembled beforecorrecting the sector header. Thus, position information of a sector,which is included in the sector header as a sector address, is detected,thus facilitating rapid access to a desired sector. This is to becompared with a conventional CD-ROM wherein sector header information isinterleaved in several C1 code words, thus requiring the recovery anderror correction of all of those C1 code wards before the sector headerdata can be assembled and interpreted.

FIG. 3 is a schematic representation of the manner in which therecording surface of disk 100 is divided into separate areas, referredto as the lead-in area, the program area and the lead-out area. FIG. 3also identifies the lead sector addresses of the program area and thelead-out area. In the illustrated embodiment, the sectors included inthe lead-in area exhibit negative sector addresses ending with thesector address −1 which, in hexadecimal notation is 0xFFFFFF. The sectoraddress of the first sector in the program area is identified as address0. As indicated, the length or duration of the program area is dependentupon the amount of data recorded therein and, thus, the address of thelast sector recorded in the program area is variable. It is appreciated,therefore, that the first sector address of the lead-out area isvariable and is dependent upon the length of the program area.

One embodiment of the disk configuration shown broadly in FIG. 3 isschematically illustrated in FIG. 4. Here, the TOC region, which iscomprised of one or more TOC tracks, is disposed in the lead-in areasand TOC information is recorded in sectors identified as −32 to −1.These 32 sectors of TOC information occupy a fixed position, such as asingle TOC track, in the lead-in area. The program area shown in FIG. 4is comprised of N tracks, where N is variable. The sector address of thefirst track of the program area is identified as address 0; and thetotal number of tracks included in the program area is dependent uponthe amount of information stored on the disk, and since the number ofsectors included in each track likewise is variable, the sectoraddresses of the lead sectors of tracks 2, 3, . . . N are variable. Ofcourse, the lead-out area commences after the Nth track is recorded.

In one embodiment, the data recorded on a given disk may admit ofdifferent applications. However, it is preferred that all of the datarecorded in a respective track admit of the same application.

FIG. 5 illustrates another disk configuration wherein TOC information isrecorded in the lead-in area from, for example, sector −32 to sector −1,as was the case in FIG. 4, and a copy of the TOC information is recordedin the program area. In the example shown in FIG. 5, the copy of the TOCinformation is recorded in at least one track whose lead sector is, forexample, sector number 1024. Since the size of the TOC region is fixedat 32 sectors, as will be described, the last sector of the copied TOCregion is sector 1055; and the lead sector of the next-following userdata track is identified as sector 1056. One reason for providing a copyof the TOC information in the program area is that some computerapplications do not easily recognize data recorded in sectors havingnegative addresses (such as sectors −32 to −1 of the TOC informationrecorded in the lead-in area).

Still another embodiment of the data configuration recorded on theoptical disk is illustrated in FIG. 6, wherein the TOC region isprovided in the program area at sectors 0 to 31. Here, the recording ofTOC information in the program area differs from the recording of TOCinformation in the program area of FIG. 5 in that the FIG. 6 arrangementdoes not include a copy of the TOC information. Nevertheless, since theTOC information is recorded in positive sector addresses in FIG. 6, thepossibility of misinterpretation due to the difficulty of recognizingnegative sector addresses by a computer is obviated.

In the embodiments of FIGS. 5 and 6 wherein TOC information is recordedin the program area, it is appreciated that the TOC region is segregatedfrom data files which are particularly relevant to the computer withwhich the optical disk is to be used. FIG. 7 illustrates a still furtherexample of the data configuration recorded on the optical disk andillustrates the TOC region to be located from sector address 32 tosector address 63. In this arrangement, information recorded in sectors0 to 31 is reserved for computer files that are particularly applicableto the computer system with which the optical disk is to be used. Thus,in the embodiments of FIGS. 5, 6 and 7 wherein TOC information isrecorded in the program area, such TOC information is segregated fromand, thus, does not interfere with file system data that may be recordedon the disk. Such file system data may occupy several sectors or severaltens of sectors; and since the TOC information is recorded in a fixednumber of sectors so as to occupy a fixed TOC region, there is nointerference by the TOC information with such file system data.

As mentioned above, in the preferred embodiment TOC information isrecorded in 32 sectors. Preferably, although not necessarily, eachsector is comprised of 2048 bytes and an example of the TOC informationrecorded in a TOC region is set out in the following Table 1.

TABLE 1 Table of Contents Information Field Name Bytes Disc Information2048  Track information (1-st Track) 32 Track Information (2-nd Track)32 Track Information (3-rd Track) 32 . . . Track Information (N-thTrack) 32 Reserved 63488-32N TOTAL 65536  

From the foregoing table, it is appreciated that the TOC informationincludes one sector dedicated to disk information, described moreparticularly with respect to Table 2, and up to 31 sectors in whichtrack information (see Table 3) is recorded. The TOC region alsoincludes a reserved area for the recording of information that may beuseful in the future. In a practical adaptation of the optical disk ofthe present invention, user information may be recorded in N trackswhere, for example, N=256. The track information which is recorded inthe TOC region relates to the data that is recorded only in acorresponding track, as will be described in conjunction with Table 3.

The data which constitutes the disk information recorded in the TOCregion is shown in the following Table 2:

TABLE 2 Disk Information Field Name Byte(s) HD-CD ID 8 Disk Type 1Reserved for Disk Size 1 Lead Out Sector Address 3 Reserved for MultiSession Parameters 20  Reserved for Writable Parameters 20  VolumeNumber 1 Total Volume Number 1 Catalog Number 16  Reserved forApplication ID Strings 8 Disk Title in English/ISO646 16  Local LanguageCountry Code 3 Length of Disk Title in Local Lan. (=N) 1 Disk Title inLocal Lang. N First Track Number 1 No. of Track Entry 1 Reserved 1947-NTOTAL 2048  The fields which identify the disk information are described moreparticularly as follows:HD-CD ID

This field, comprised of 8 bytes, contains a character string thatidentifies the data structure recorded on the disk, including the datastructure which is used to represent TOC information, the data structureused to represent track information and the data structure of a sector.For example, if the character string is “HD-CD001”, the data structurerecorded on the disk is of the type illustrated in FIG. 4, the datastructure used to represent TOC information is as shown in Table 1, thedata structure used to represent track information is as shown in Tables2 and 3 and the data structure of the sectors of, for example, the userdata tracks, is as shown in Table 4 (to be described). Different datastructures may be identified by the character string “HD-CD002”,“HD-CD003”, etc. The particular character string which is recorded inthis field is detected by the reproducing apparatus which permits properinterpretation of the played back data consistent with the sensed datastructure.

Disk Type

This 1-byte data identifies the type of disk as, for example, a readonly disk, a write once read many (WORM) disk or an erasable disk (suchas the writable optical disk known as the “Mini” disc).

Reserved For Disk Size

This 1-byte field is used to identify the size of the optical disk. Forexample, a disk diameter of 120 millimeters may be identified by a bytewhose value is “1”, a disk whose diameter is 80 millimeters may beidentified by a byte whose value is “2”, and so on. In addition or,alternatively, this field may be used to identify the storage capacityof the disk.

Lead Out Sector Address

This 3-byte field identifies the address of the first sector in thelead-out area

Reserved For Multisession and Writable Parameters

These two-fields, each formed of 20 bytes, store information which isparticularly useful for erasable disks or for WORM disks and is notfurther described herein.

Volume Number

This 1-byte data field is used when several disks constitute acollection of data for a particular application. For example, if thecollection includes 2, 3, 4, etc. disks, this field identifies which oneof those disks is the present disk.

Total Volume Number

This 1-byte field identifies the total number of disks which constitutethe collection in which the present disk is included.

Catalog Number

This 16-byte field is used to identify the type of information orprogram that is recorded on the disk. Such identification constitutesthe “catalog number” and is represented as UPC/EAN/JAN code presentlyused to identify various goods.

Reserved For Application ID Strings

This 8-byte field is intended to identify the particular userapplication for this disk medium. At present, this field is not used.

Disk Title In English/ISO646

This 16-byte field stores the title of the disk in the English language,as represented by the ISO646 standard. Although the actual title of thedisk may be in another language, its English translation or acorresponding English identification of that title is recorded in thisfield. In other embodiments, the field may contain a lesser or greaternumber of bytes so as to accommodate English titles of lesser or greaterlength.

Local Language Country Code

This 3-byte field is intended to identify the actual language of thetitle of the disk. For example, if the actual title of the disk is inJapanese, this field records the “local language country” as Japan. Ifthe title is in French, this field records the “local language country”as France. The code recorded in this field may exhibit a numerical valuecorresponding to a particular country or, alternatively, the field maybe as prescribed by the ISO3166 standard. If it is desired not toutilize this field, the character string recorded therein may be0xFFFFFF.

Length of Disk Title in Local Language

This 1-byte field identifies the number of bytes that are used in the“Disk Title In Local Language” field (to be described) to represent thetitle of the disk in the local language. If the actual disk title is notrecorded in a language other than English, the “Disk Title In LocalLanguage” field is left blank and the numerical value of this “Length OfDisk Title In Local Language” field is 0.

Disk Title In Local Language

This N-byte field represents the actual title of the disk in the locallanguage. It is expected that different languages will adopt differentstandards to represent disk titles, and such local language standardsare expected to be used as the data recorded in this field. It isappreciated that the number of bytes which constitute this field isvariable.

First Track Number

This 1-byte field identifies the number of the track which constitutesthe first track that contains user information. For example, if the TOCinformation is recorded in a single track, and if this single track isidentified as track 0 in the program area, then the number of the trackwhich constitutes the “First Track Number” is 1.

Number of Track Entries

This 1-byte field identifies the total number of user tracks that arerecorded. It is appreciated that if this field contains a single byte, amaximum of 256 user data tracks, that is, tracks which contain userinformation, may be recorded.

The data recorded in the track information fields of the TOC data shownin Table 1 now will be described in conjunction with the following Table3:

TABLE 3 Track Information Field Name Byte(s) Track Number 1 ECC Type 1Speed Setting 1 Start SA 3 End SA 3 Time Code at Start Point 4 PlayingTime 4 Mastering Date & Time 7 Reserved for Application ID Strings 8TOTAL 32

The information recorded in each of the fields which constitute thetrack information of Table 3 now will be described in greater detail.

Track Number

This 1-byte field identifies the number of the track represented by thistrack information. Since one byte is used to identify the track number,it is appreciated that a maximum of 256 user data tracks may berecorded. Of course, a single track number is used to identify arespective track, and no two tracks on this disk are identified by thesame track number. Although it is preferred that the successive tracksare numbered sequentially, it also is appreciated that, if desired, eachtrack may be assigned a random number and this random number isidentified by the “Track Number” field.

ECC Type

This 1-byte data identifies the error correction code which is used toencode the user data recorded in this track. For example, the ECC typemay be either long distance error correction code, known as the Lformat, or short distance error correction code, known as the S format.The difference between the L format and the S format is described below.

Speed Setting

This 1-byte data identifies the data transfer rate by which data isrecovered from this track. For example, if a reference data transferrate is 1.4 Mbps, the “Speed Setting” field may exhibit a valuerepresenting 1× this reference rate or 2× the reference rate or 4× thereference rate or 6× the reference rate. FIG. 8 is a tabularrepresentation of this “Speed Setting” field; and it is appreciated thatthe data transfer rate need not be an integral multiple of the referencedata transfer rate, as represented by the value “FF”. The byte value 0for this field, as shown in FIG. 8, represents that real time read-outof data is not required. It is appreciated that computer data, asopposed to, for example, video data, does not require real timeread-out. Hence, if computer data is recorded in the track identified bythe “Track Number” field in Table 3. the value of the “Speed Setting”field is set to 0.

Start and End Sector Addresses (SA)

These 3-byte fields identify the address of the start sector of thetrack identified in the “Track Number” field and the address of the endsector of that track Since the number of sectors included in a track isvariable, the start and end sector addresses of a given track are notfixed. Hence, these fields are useful when carrying out a high speedaccess operation of a desired track.

Time Code At Start Point

This 4-byte field identifies a time code for the start sector in thetrack identified by the “Track Number” field. It will be appreciatedthat if the user information represents video data, such video data maybe recorded with conventional time codes and the start sector of thetrack which contains such video data is recorded in this “Time Code AtStart Point” field. If time codes are not recorded with the userinformation, this field may be left blank or may be provided with nodata, such as the character code 0.

Playing Time

This 4-byte data represents the overall playback time for the programinformation that is recorded in the track identified by the “TrackNumber” field. For example, if the user information in this track is anaudio program, the playing time for this track may be on the order ofabout 10 minutes. If the user information constitutes compressed videodata, the playing time may be 2 or 3 or even up to 15 minutes.

Mastering Date and Time

This 7-byte field identifies the date and time of creation of the masterdisk from which this optical disk was made. FIG. 9 is a tabularrepresentation of this field. If desired, this field may be replaced bynull data represented by character code 0.

Reserved For Application ID Strings

This 8-byte field is intended to store information representative of theparticular application for which the data record in the track identifiedby the “Track Number” field is to be used. This differs slightly fromthe “Application ID” field in Table 2 because the Table 2 field isintended to identify the type of application or use intended for theentire disk, whereas the “Application ID” field of Table 3 simply theidentifies the type or use of the data recorded in a particular track onthat disk.

Referring now to FIG. 10, there is illustrated a preferred embodiment ofthe data structure of a sector of user information. TOC information alsois recorded in sectors, and the structure of such TOC sector is similar.The following Table 4 identifies the fields of the sectors shown in FIG.10:

TABLE 4 Sector Construction Field Name Byte(s) Sector Sync 4 CRC 2Subcode 5 Pos-in-Cluster 1 Address 3 Mode 1 Sub-Header 8 User Data 2048EDC 4 Reserved 12 TOTAL 2088

It is seen that a sector is comprised of a sector header which contains24-bytes arranged as shown in FIG. 10, followed by 2.048 bytes of userdata, 4-bytes of error detection code (EDC) and 12-bytes which arereserved. Preferably, a number of sectors constitute a “cluster”, and asone example, a cluster is comprised of 8 sectors or 16 sectors, as maybe determined by the preferred format.

A more detailed explanation of the different fields which constitute thesector shown in FIG. 10 now will be provided.

Sector Sync

This 4-byte field is formed of a predetermined bit pattern which isreadily detected and which is unique and distinctive from the datapattern included in any other field of a sector. The accurate detectionof the sync pattern may be confirmed sensing errors which areinterpretated from the information reproduced from the sector. If alarge number of errors are detected continually, it is safely assumedthat the sync pattern has not been accurately sensed. Alternatively, andpreferably, the demodulator which is used to convert 16-bit symbols to8-bit bytes (or, more generally, to convert an m-bit symbol to an n-bitbyte) may include suitable conversion tables which are not operable toconvert the sync pattern to a byte. The sync pattern is assumed to bepresent when the demodulator is unable to find an n-bit byte whichcorresponds to a received m-bit symbol.

Cyclic Redundancy Code (CRC)

This 2-byte field is derived from the subcode data, the cluster positiondata and the sector address and mode data included in the sector header.Such CRC data is used to correct errors that may be present in thesefields.

Subcode

This 5-byte field is described below.

Cluster Position

This 1-byte field identifies the particular order in the cluster inwhich this sector is located. For example, if the cluster is formed of a8 sectors, this field identifies the particular sector as the first,second, third, etc. sector in the cluster.

Address

This 3-byte field constitutes the unique address for this sector. Sincethe address is represented as 3-bytes, a maximum of 64K sectorstheoretically may be recorded. FIGS. 4–7 represent the sector addressesof different user data tracks.

Mode and Sub-Header

These fields are conventionally used in CD-ROMs and the data representedhere is the same as that conventionally used in such CD-ROMs.

User Data

2,048 bytes of information are recorded in the user data field. Forexample, computer data compressed video data, audio data and the likemay be recorded. If video data is recorded, the MPEG standard may beused to compress that data as described in standard ISO1381-1.

Error Detection Code

This 4-byte data is cyclic code which is added by EDC adder 127 (FIG. 1)and is used to enable the detection of an uncorrectable error in thesector.

A detailed discussion of the sub-code field now is provided inconjunction with FIGS. 11A–11E. It is appreciated that the sub-codefield is comprised of two portions: a 1-byte address portion and a4-byte data portion. The value of the address portion serves to identifythe type of data that is recorded in the data portion. For example, andas shown in FIG. 11A, if the value of the address portion is 0, null orzero data is recorded in the data portion.

If the value of the address portion is 1, as shown in FIG. 11B, the dataportion is provided with the following 1-byte information:

Track Number

This data identifies the number of the track in which the sectorcontaining this sub-code is recorded.

Copyrighted

This byte exhibits the structure shown in FIG. 12 wherein a “1” bitrepresents that copying of the associated user data is prohibited and a“0” bit indicates that copying of the associated data is permitted. Thebit positions of the copyright byte identify the type of user data forwhich copying is selectively prohibited or permitted. As shown in FIG.12, the identified user data is analog video data, analog audio data,digital video data, digital audio data, and the like. For example, ifthe user data in this sector is digital video data and if copying ofthat digital video data is prohibited, the copyright byte may appear as“00100000”.

Application ID

This indicates the particular application intended for the user datathat is recorded in this sector. Examples of typical applications areshown in FIG. 13 as computer text, video, video/audio, etc. If no datais recorded in this sector, the application ID byte may be representedas the character 0.

ECC Type

This data indicates whether the user data is ECC encoded in, forexample, the L format or the S format, as shown in FIG. 16. Other typesof ECC codes may be represented by other values of this ECC type byte.

If the value of the sub-code address is 2, as represented in FIG. 11C,the data portion represents time code. That is, if the user datarecorded in this sector is variable over time, as would be the case ifsuch data is video data, the time code data recorded in the sub-codefield represents time information at which the user data is recorded. Anexample of such time code data is represented in FIG. 14. It isappreciated that 2-digit BCD bits are used to represent the hour,minute, second and frame at which the user data in this sector isrecorded.

If the value of the address portion is 3, as depicted in FIG. 11D, thedata portion of the sub-code field represents the distance from thesector in which this sub-code field is recorded to the first sector inwhich an immediately preceding I compressed video picture is recorded;and also the distance from this sector to the first sector in which thenext-following I compressed video picture is recorded. Those of ordinaryskill in the art will recognize that video data, when compressed inaccordance with the MPEG standard, may constitute an intraframe encodedvideo picture, typically known as an I picture, a predictive coded videopicture, typically known as a P picture, and a bi-directionallypredictive coded video picture, typically known as a B picture. The dataportion of the sub-code field whose address portion has the value of 3thus indicates the distances between this sector and the beginning ofthe next-preceding and next-following I pictures.

If the value of the address portion is 4, as shown in FIG. 11E, the dataportion includes 1-byte picture type, indicating whether the videopicture that is recorded in this sector is an I, P, or B picture (seeFIGS. 15), and 2-byte temporal reference data which indicates thelocation in the original picture display sequence of the particularpicture that is recorded in this sector. This temporal reference data ishelpful during a playback operation because, as those of ordinary skillin the art recognize, the location of compressed B-picture data in theMPEG code sequence may be quite different from the actual location ofthat picture when the B-picture ultimately is displayed.

The ECC format which preferably is used with the present invention isthe L format. A schematic representation of an encoded “data frame” isdepicted in FIG. 17. The ECC “frame” is referred to herein as a C1 codeword and this word when recorded, consists of a sync pattern followed by136 data symbols. The term “symbol” is used rather than “byte” because,as will be described, the recorded “symbol” consists of 16 bits (knownas channel bits), whereas a byte typically is understood to consist ofonly 8 bits. It is appreciated, however, that the C1 code word, prior toconversion from 8-bit bytes to 16-bit symbols, that is, prior tomodulation of the C1 code word, nevertheless consists of theconstruction shown in FIG. 17, wherein it will be understood that theillustrated symbols are, in fact, bytes.

The manner in which the C1 code word structure is generated now will bebriefly described, 116 data bytes, or symbols, known as a C2 word, aresupplied to, for example, the ECC encoder formed of memory 131 and ECCcircuit 132 of FIG. 1. A C2 hold section is added to the C2 word,preferably by being inserted between two groups of 58 symbols, and a C1hold section is added to the end of the resultant 128 symbols. A holdsection merely reserves a location in the data stream in which paritydata subsequently is inserted. Thus, a preliminary C1 word may bethought of as being formed of a group of 58 data symbols followed by aC2 hold section followed by a group of 58 data symbols followed by a C1hold section. Then, C2 parity symbols are generated by, for example,modulo 2 addition. Preferably, one data symbol in one preliminary C1word is modulo-2 combined with a data symbol included in the next (orsecond) preliminary C1 word. If desired, further combinations may beeffected with a data symbol included in the third-following preliminaryC1 word, and so on, to produce one C2 parity symbol. The next C2 paritysymbol is produced by a similar combination of the next data symbol inthis first preliminary C1 word with respective data symbols in thenext-following preliminary C1 words. In this manner, C2 parity symbolsare generated by combining a predetermined number of data symbols of thesame predetermined number of successive preliminary C1 words. That is,if the C2 parity symbol is produced by modulo-2 combining two datawords, then one data word of the first preliminary C1 word is modulo-2combined with one data symbol in the next symbol position of thenext-following preliminary C1 word. If the C2 parity symbol is producedby combining three data symbols, then one data symbol in successivesymbol positions from each of three successive preliminary C1 words arecombined to produce the C2 parity symbol. And if the C2 parity symbol isgenerated by combining four data symbols, than one data symbol insuccessive symbol positions from each of four successive preliminary C1words are combined.

As a preferred aspect of this ECC encoding, the data symbols which arecombined occupy successive positions in the respective preliminary C1words. That is, if the data symbol in the first preliminary C1 word isthe nth data symbol, the data symbol in the second preliminary C1 wordis the (nth+1)th data symbol, the data symbol in the third preliminaryC1 word is the (n+2)th data symbol, and so on.

When 12 C2 parity symbols are generated in the manner just described,those 12 C2 parity symbols are inserted into the C2 hold section of thisfirst preliminary C1 word, thus forming a precursory C1 word. Then, 8 C1parity symbols are generated by conventional parity symbol generation inresponse to the data and parity symbols included in this precursory C1word. The generated C1 parity symbols are inserted into the C1 holdsection thus forming the C1 code word.

In the C1 code word shown in FIG. 17, the C2 parity symbols are insertedbetween two groups of data symbols. Alternatively, the C2 parity symbolsmay be located at the end of the 116 data symbols, that is, at the endof the C2 word. A preestablished number of C1 code words having thestructure shown in FIG. 17 constitute the long distance error correctionencoded data. That is, a preestablished number of the C1 code words areused as the L format ECC encoded data having the structure shown in FIG.18. As illustrated, 128 C1 code words are used, such that i=0, 1 . . .127. Each C1 code word is comprised of a sync code, or pattern. followedby 136 symbols S₀, S₁, . . . S_(j) . . . S₁₃₅, wherein j=0, 1 . . . 135.The circles shown in FIG. 18 represent the manner in which the C2 paritysymbols are generated. As has been described above, the C2 paritysymbols are generated for the C1₀ code word in response to the datasymbols included in code words C1₀, C1₁ . . . C1_(r), where r representsthe number of data symbols and that are combined to generate the paritysymbol. From FIGS. 17 and 18, it is seen that symbols S₀–S₁₂₇ constitutedata and C2 parity symbols, and symbols S₁₂₈–S₁₃₅ constitute C1 paritysymbols. It will be appreciated that, since twelve C2 parity symbols arerecorded in a C1 code word, up to twelve data symbols can be corrected.Since these twelve data symbols are included in twelve successive C1code words, a burst error of twelve C1 code words can be corrected,which amounts to a correctable error of 12×136=1,632 symbols.

An example of the S format ECC encoding is schematically illustrated inFIG. 19. In the S format, the twelve C2 parity symbols are divided intotwo groups of six C2 parity symbols each, with one group of six C2parity symbols being added to 58 data symbols and the other group of sixC2 parity symbols being added to the next 58 data symbols. Thus, ratherthan generating the C2 parity symbols from data symbols included in 128C1 code words, the C2 parity symbols in the S format are generated fromsuccessive data symbols included in 64 C1 code words having theschematic representation shown in FIG. 19. Whereas the L format permitsthe use of C2 parity symbols to correct errors in twelve C1 code words,the S format supports C2 parity correction of up to six C1 code words.Hence, the S format permits the correction of a burst error of 6×136=816symbols.

When compared to the ECC format used in, for example, CD-ROMs of typethat have been proposed heretofore, the use of the L format or S formatin accordance with the present invention permits a reduction inredundancy from about 25% of prior art CD-ROMs to about 15% in thepresent invention.

A sector formed of ECC encoded data in the L format or the S format isshown in FIG. 21 wherein the sector includes a sector header formed of24 symbols and also is comprised of eighteen C1 code words, each C1 codeword having the construction shown in FIG. 17. The last C1 code wordincluded in the sector includes four error detection code symbols andtwelve symbols that are reserved for future use. The sector headerexhibits the structure shown in FIG. 10. Nevertheless, errors that maybe present in the sector header can be corrected generally by using onlythe C1 parity symbols which are generated for that C1 code word.

As an aspect of this invention, the sequence of the symbols included ina C1 code word as recorded in a track differs from the sequence of thesymbols that are supplied for recording. That is, and with reference toFIG. 1, the sequence of the symbols supplied to modulator 140 differsfrom the sequence of symbols supplied to switch 124. By recording thedata symbols in what is referred to herein as a disarranged order, thepossibility is reduced that a burst error will destroy the data to theextent that, when reproduced, the data will not be interpretable. Inparticular, if the data represents video information, the recording ofthe data symbols in disarranged order enhances the possibility thataccurate video pictures nevertheless can be recovered even in thepresence of the burst error. FIG. 20 is a schematic representation ofthe manner in which the data symbols are disarranged for recording.

Let it be assumed that data symbols are recorded on the disk in theorder D_(k) and let it be further assumed that each C1 code word isformed of m symbols, with n of those symbols constituting a C2 code word(i.e. 116 data symbols and 12 C2 parity symbols) and m–n of thosesymbols constituting the C1 parity symbols. The relationship among i, j,k, m and n for recording thus is:k=m×i+2×j−m, when j<m/2k=m×i+2×j−(m−1) when j≧m/2If the data symbols appear on the disk in the recorded sequence D₀, D₁,D₂ . . . such data symbols are grouped into an odd group followed by aneven group. For example, and assuming 136 symbols, data symbols D₀–D₆₇constitute an odd group of odd numbered data symbols and data symbolsD₆₈–D₁₃₅ constitute an even group of even data symbols. It will beunderstood that “odd” and “even” refer to the original sequence in whichthose data symbols had been presented for recording. In the foregoingequations, i is the sequential order in which the C1 code words arepresented for recording, j is the sequential order of the m symbols ineach C1 code word presented for recording and k is the order in whichthe m symbols are recorded on the disk. That is, D_(j)≠D_(k).

When the C1 code words having data symbols in the sequence D₀, D₁, . . .D₁₃₅ are played back from the disk, the data symbols stored in ringbuffer 217 of FIG. 2 are rearranged to the sequence illustrated in FIG.20. This sequence of FIG. 20 is referred to as the arranged sequence andis formed of sequential alternating odd and even data symbols which isthe same sequence as the data symbols originally presented to switch 124of FIG. 1 for recording. It will be appreciated that the data symbolswhich are included in the recorded C1₁ code word in fact belong in partto C1₀ code word and the C1₁ code word. That is, if the C1₁ recordedcode word is formed of symbols D₀, D₁, . . . D₁₃₅, the reproduced C1₀code word includes symbols D₁, D₃, . . . D₁₃₃, D₁₃₅ and the reproducedC1₁ code word includes symbols D₀, D₂, . . . D₁₃₂, D₁₃₄. The sequentialstorage positions in ring buffer 217 of FIG. 2 of the symbols D_(k) thatare reproduced from the disk may be expressed as follows:i=(k/m)−(kmod2)+1j=(m/2)×(kmod2)+(kmodm)/2where i is the sequential order of the C1 code words that are read outof the ring buffer, j is the sequential order of the sequence of the msymbols in each C1 code word that is read out of the ring buffer and kis the disarranged order in which the m symbols are recorded on thedisk.

Although the present invention preferably records data in the L formatof ECC encoding, the teachings herein may be employed with S format ECCencoding. Discrimination between the L format and S format may be madeby sensing the ECC byte in the track information field of the TOC data,such as the ECC byte shown in Table 3, or by sensing the ECC byteincluded in the subcode field shown in FIG. 11B, wherein the ECC byte ofthe subcode field may have the structure shown in FIG. 16. Anothertechnique that can be used for ECC format discrimination contemplatesusing one type of sector sync patter when L format ECC encoding is usedand another type of sector sync pattern when S format ECC encoding isused. Thus, not only is sector synchronization detected but, at the sametime, the type of ECC format is sensed.

Yet another technique for discriminating between L format and S formatECC encoding employs the addition of a discrimination bit immediatelyfollowing the sector sync pattern.

Still another technique for discriminating between the L and S ECCformats is based upon the ability of the ECC correcting circuit 216 ofFIG. 2 to operate satisfactorily. For example, if error correctionassumes that the ECC encoded data is in the L format and errorcorrection is not possible, it is highly likely that the data actuallyis in the S format. Conversely, if error correction assumes that the ECCencoded data is in the S format but error correction is not possible, itis highly likely that the data had been encoded in the L format. Thus,discrimination between the formats is dependent upon the success orfailure of error correction.

The ECC encoded data, whether in the L format or the S format,constitute convolution codes. A group of C1 code words may be thought ofas a block and such C1 code words may be block coded in the manner shownschematically in FIG. 22. Here, in addition to L format ECC encoding,the C1 code words are block coded as will now be briefly described. Letit be assumed that the data symbols in a preliminary C1 word constitutea C2 word (as described above). Let it be assumed that the C2 words arepresented in the sequence C2₁, C2₂, C2₃, etc. In FIG. 22, the symbolsrepresented by an open circle are data symbols included in the C2₀ word,the symbols represented by a filled-in circle are data symbols includedin the C2₁₆ word, the symbols represented by a triangle are data symbolsincluded in the C2₁₇ word, the symbols represented by a square are datasymbols included in the C2₁₈ word, and the symbols represented by an Xare data symbols included in the C2₁₉ word. Since a block code consistsof 144 C1 code words, but each C1 code word includes only 128 datasymbols (including C2 parity symbols) it follows that one data symbol inthe C1₁₇ code word cannot be included in the illustrated block and isexpected to be included in the next-following block. However, blockcoding requires all of the data symbols in a block of code wordsC1₀–C1₁₄₃ to remain in that block and, therefore, the last data symbolof the C1₁₇ code word is “folded back” into this block as the last datasymbol of the C1₀ code word. Similarly, the last two data symbols of theC1₈ word are expected to fall within the next-following block, butbecause of block coding, these two symbols, identified as data symbols126 and 127, are folded back into the C1₀ and C1₁ code words,respectively. Stated generally, those data symbols of a C2 word whichotherwise would be included in the next-following block are folded backto the beginning of the illustrated block such that each C1 code wordincluded in a block of 144 C1 code words includes interleaved datasymbols from 128 of the 144 C1 code words, as shown.

Each block consists of 8 sectors, whereby a block includes more than 16Kbytes. Error correction can be carried out on a block-by-block basis.

FIG. 23 is a schematic representation of the block coding of S formatECC encoded data. The same principle that is used for the block codingof L format ECC encoded data, as discussed in conjunction with FIG. 22,is applicable to the block coding of S format ECC encoded data. Here,however, each block consists of 4 sectors; and as a result, each blockis comprised of more than 8K bytes.

The modulation technique used to modulate the C1 code words forrecording on disc 100 (e.g., the modulation technique used by modulator140 of FIG. 1) now will be described.

One type of modulation is 8-to-14 modulation (EFM) which is used as thestandard in compact discs, and one example of such EFM processing isdescribed in Japanese patent application 6-2655. In conventional EFM, an8-bit byte is converted into a 14-bit symbol (the bits of the symbolsare known as “channel” bits because they are supplied to the recordingchannel) and successive symbols are separated by margin bits. Heretoforethree margin bits were used, and these three bits were selected toassure that the Digital Sum Value (DSV) accumulated from successivesymbols is reduced. EFM is a run length limited (RLL) code and,preferably, the shortest run length permitted in EFM consists of twoconsecutive zeros which are spaced between is, and the longest runlength is limited to 10, wherein 10 consecutive zeros may be presentbetween is.

If two margin bits are used rather than 3, the possible combinations ofsuch margin bits are: 00, 01, 10 and 11. In EFM, a margin bit state 11is prohibited. Hence, only three different combinations of margin bitscan be used to link (or separate) successive symbols: 00, 01 and 10.But, depending upon the bit stream of one or the other symbols which arelinked by the margin bits, one or more of these possible states may beprecluded because, to use the precluded state may result in anundesirable DSV.

FIG. 24 is a schematic representation of a “string” of data symbolsseparated by margin bits. Each data symbol is comprised of 14 channelbits and the margin bits are comprised of 2 channel bits. Thus, marginbits M₁ separate data symbols D₁ and D₂; margin bits M₂ separate datasymbols D₂ and D₃; margin bits M₃ separate data symbols D₃ and D₄, andso on, with margin bits M_(m) separating data symbols D_(m) and D_(m+1).Nevertheless, assuming that the 14 channel bits included in a datasymbol are provided in 14 successive bit cells and further assuming thatthe margin bits are included in 2 successive bit cells, successive datatransitions in the string of channel bits depicted in FIG. 24 areseparated by no less than 2 data bit cells and by no more than 10 databit cells.

A string of data symbols may include parity symbols, and FIG. 27illustrates a frame of such symbols beginning with a sync pattern of 24bit cells, followed by 12 data symbols (shown as 14-bit symbolsseparated by 2 channel bits), followed by 4 parity symbols, followed by12 data symbols and ending with 4 parity symbols. The sync pattern isillustrated as a high signal level extending for 11 bit cells followedby a low signal level extending for 11 bit cells, followed by a highsignal level extending for 2 bit cells. The inverse of this pattern canbe used FIG. 27 also depicts the two-bit margin bits which separatesuccessive data symbols; and as mentioned above, in some instances,certain ones of as the three permitted combinations of margin bitscannot be used. FIG. 28 schematically represents the conditions underwhich the margin bit combination 00 or the margin bit combination 01 orthe margin bit combination 10 cannot be used. As will described, asignal known as the inhibit margin bit signal M identifies the marginbit combination which cannot be used. For example, when M_(inh)=00, themargin bit combination 00 cannot be used. Similarly, when M_(inh)=01,the margin bit combination 01 cannot be used. And when M_(inh)=10, themargin bit combination 10 cannot be used.

Let it be assumed that margin bits separate data symbols D₁ and D₂. Letit be further assumed that the number of consecutive zeros at theleading end of data symbol D₂ is represented as A and the number ofzeros at the terminating end of data symbol D₁ is B. If A+B is equal toor exceeds 8 successive zeros (A+B≧8) then the margin bit combination 00is inhibited (M_(inh)=00).

If the most significant bit C1 of data symbol D₂ is “1” (A=0) or if thenext most significant bit C2 is “1” (A=1) or if the least significantbit C14 of data symbol D₁ is “1”, the margin bit combination 01 isinhibited (M_(inh)=01).

If the least significant bit C14 of data symbol D₁ is “1” (B=0) or ifthe next least significant bit C13 is “1” (B=1), or if the mostsignificant bit C1 of data symbol D₁ is “1”, the margin bit combination10 is inhibited (M_(inh)=10).

The foregoing 3 conditions are not mutually exclusive; and from FIG. 28it is seen that conditions may exist which preclude the margin bitcombinations 01 and 10 (both margin bit conditions are precluded if themost significant bit C1 of data symbol D₂ is “1” or if the leastsignificant bit C14 of data symbol D₁ is “1”). The number of inhibitmargin bit combinations is represented as NI. If NI=0, all three marginbit combinations may be used. If NI=1, one of the three margin bitpatterns is precluded and the other two may be used. If NI=2, two of themargin bit patterns are precluded but the third is permitted. It will beappreciated that NI never is three.

Turning now to FIG. 25, there is illustrated a flow chart whichrepresents the manner in which a margin bit combination is selected forinsertion by a margin bit generator between two data symbols. At stepS1, the inhibited margin bit combinations are determined for each set ofmargin bits M₁, M₂ . . . M_(m) and the number of inhibited margin bitcombinations NI₁, NI₂, . . . NI_(m) likewise is determined. It will beappreciated that M_(inh) and NI for each set of margin bits to beinserted between data symbols may be determined from the conditionsdepicted in FIG. 28.

The flow chart then advances to inquiry S2 which determines if thenumber of inhibited combinations for the margin bit pattern M₁ is equalto 2. If so, the flow chart advances to step S3 and only a single marginbit combination can be selected. For example, if the most significantbit of data symbol D₂ is “1”, NI₁=2 and M_(inh)=01, 10. Step S3 thuspermits only margin bit combinations 00 to be selected as the margin bitpattern M₁.

However, if inquiry S2 is answered in the negative, then two or threedifferent margin bit combinations can be selected. The flow chartadvances to step S4 where the inhibited margin bit combination Minh forthe n-th margin bit pattern (n72) is determined. But, if the number ofinhibited combinations for the second margin bit pattern is 2, that is,if NI₂=2, then the n-th margin bit pattern is construed as the (m+1)thmargin bit pattern. That is, if NI₂=2, only one margin bit combinationcan be selected for the remaining margin bit patterns M_(n). The flowchart then advances to step S5 wherein data symbol D₂ is linked to datasymbol D₃ which is linked to data symbol D₄. . . to data symbol D_(n) bythe respective margin bit combinations which are not inhibited.

Thereafter, in step S6, since the margin bit patterns up to M_(n) havebeen selected, and since the data symbols up to D_(n) are known, theaccumulated DSV up to D_(n) is calculated. The DSV determined for thisdata symbol simply is added to the DSV which has been accumulated fromprevious data symbols. Then, in step S7, the margin bit pattern M₁ isselected as the particular margin bit combination which minimizes theDSV that is projected to be accumulated up to data symbol D_(n).

It will be appreciated that steps S4–S7 rely upon a projected DSV; andalthough the margin bit pattern under consideration is margin patternM₁, the technique for selecting the appropriate margin bit combinationfor pattern M₁ as based upon look ahead data symbols D₂, D₃, . . .D_(n). FIG. 29 is a graphical representation of the manner in which theprojected DSV is accumulated based upon “look ahead” data symbols. Forsimplification, it is assumed that m=3, that data symbols D₁, D₂ and D₃are known, that the accumulated DSV up to data symbol D₁ is known andthat margin bit pattern M₁ is to be selected. FIG. 29A represents the14-bit data symbol, wherein a “1” is represented by a transition and a“0” is represented by no transition in the digital signal. The datasymbols shown in FIG. 29A are the same data signals used in FIGS. 29Band 29C. FIG. 29A represents the margin bit pattern M₁ as thecombination 10; FIG. 29B represents the margin bit pattern M₁ as thecombination 01 and FIG. 29C represents the margin bit pattern M₁ as thecombination 00. It is assumed that NI₁=0, meaning that there are noinhibited margin bit combinations for margin bit pattern M. It isfurther assumed that the least significant bit of a data symbol isrepresented as “CWLL” and CWLL=0 in each of data symbols D₁, D₂ and D₃.Furthermore, based upon the most significant bit of data symbol D₃,margin bit combinations 01 and 10 are inhibited (see FIG. 28) and NI₂=2.Finally, based upon the bit stream of the trailing end of data symbol D₃and the bit stream at the leading end of data symbol D₄, margin bitcombination 00 is inhibited for M₃ (see FIG. 28) and NI₃=1.

FIG. 29D illustrates the accumulated DSV that is obtained up to the endof data symbol D₃ if M₁=0, if M₁=01 and if M₁=00. In particular, curve aof FIG. 29D illustrates the accumulated DSV when M₁=10; curve brepresents the accumulated DSV when M₁=01; and curve c represents theaccumulated DSV when M₁=00. It is seen that at the end of data symbolD₂, DSV=3 if M₁=10; DSV=1 if M₁=01; and DSV=−5 if M₁=00. Thus, tominimize the accumulated DSV, the margin bit combination 01 should beselected for margin bit pattern M₁. But, if the margin bit combination01 is selected, the accumulated DSV at the end of data symbol D₃ is seento be DSV=−5. On the other hand, if the margin bit combination 00 hadbeen selected for the margin bit pattern M₁, the accumulated DSV at theend of data symbol D₃ is DSV=1. It is appreciated then, that if theprojected DSV is examined, the particular margin bit combination that isselected for margin bit pattern M₁ differs from the margin bitcombination that would be selected if the projected DSV is not examined.

FIG. 26 is a block diagram of margin bit selection apparatus in whichthe margin bit combination for margin bit pattern M₁ is determined bylooking ahead by up to m data symbols, where m=4. Thus, the accumulatedDSV up to the end of data symbol D₅ is calculated. Input terminal 10 inFIG. 26 is supplied with 32 successive bytes that have been ECC encoded,and these bytes are used to read out 14-bit symbols from a conversiontable 11 stored as a ROM. Successive 14-bit symbols are coupled to anadder 13 which adds a pseudo frame sync signal to the successive datasymbols, the pseudo frame sync signal S¹ _(f) (“1XXXXXXXXXXX10”) beingadded to the leading portion of each sync frame. The pseudo frame syncsignal serves to “reserve” a location in which the actual frame syncpattern is inserted, as will be described.

Successive data symbols are coupled to registers 14–17 wherein each datasymbol is stored. Thus, register 17 stores data symbol D₁, register 16stores data symbol D₂, register 15 stores data symbol D₃, register 14stores data symbol D₄ and adder 13 now supplies data symbol D₅ to theinput of register 14. Data symbols D₄ and D₅ are coupled todiscriminator 30 which examines these data symbols to determine if anyof the bit patterns therein correspond to those shown in FIG. 28.Depending upon the sensed bit patterns, discriminator 30 generates theinhibit margin bit signal M_(inh) which precludes certain margin bitcombinations from margin bit pattern M₄. The inhibit margin bit signalproduced by the discriminator is comprised of 3 bits and is identifiedas the margin bit inhibit signal S_(inh4). A “1” in the first bitposition of S_(inh4) inhibits the margin bit combination 10, a “1” inthe second bit position of S_(inh4) inhibits the margin bit combination01 and a “1” in the third bit position of S_(inh4) inhibits the marginbit combination 00. As an example, if only the margin bit combination 00is a permitted margin bit pattern, margin bit inhibit signal S_(inh4) isrepresented as “110”.

The output of register 17 is coupled to a frame sync converter 18 whichconverts the 14-bit pseudo frame sync signal S¹ _(f) to a 24-bit framesync signal Sf. This 24-bit frame sync signal Sf is coupled toparallel-to-serial register 19. Those data symbols D₁, D₂, . . . whichare supplied successively to frame sync converter 18 are not modifiedthereby and are supplied as is, that is, in their 14-bit configuration,to the parallel-to-serial register. Register 19 converts those bitswhich are supplied thereto in parallel to serial output form. Inaddition, after a 14-bit data symbol is serially read out of theregister, a 2-bit margin pattern produced by a margin bit generator 50is serially read out of the register. Parallel-to-serial register 19 isclocked with a channel bit clock having a frequency of 24.4314 MHz suchthat the serial bit output rate of register 19 is 24.4314 Mbps. Theseserial bits are modulated by an NRZI modulator 20 and coupled to anoutput 21 for recording.

The modulated NRZI serial bits also are fed back to a DSV integrator 40which integrates the DC component of such serial bits. The DSVintegrator thus accumulates the DSV of the data symbols and margin bitpatterns.

Margin bit generator 50 functions in accordance with the flow chartshown in FIG. 25 to effect the operation illustrated by the waveforms ofFIGS. 29A–29D. It is appreciated, then, that the margin bit generator 50may be a digital signal processor, an arithmetic logic unit or amicroprocessor programmed in accordance with the flow chart of FIG. 25.Thus, the appropriate margin bit combination is selected in order tominimize the accumulated DSV will obtain as a result of m subsequentdata symbols.

The foregoing has described an EFM technique in which a margin bitpattern is inserted between successive 14-bit data symbols. As a result,each 8-bit byte is converted into a 14-bit data symbol plus a 2-bitmargin pattern. A preferred embodiment of an 8-to-16 modulator whicheliminates the generation of margin bit patterns, which minimizes theaccumulated DSV and which is constrained to run length limited (2, 10)code now will be described. Referring to FIG. 30, a plurality of“fundamental conversion tables are provided, for example, fourconversion tables T₁, T₂, T₃ and T₄. Each fundamental table is comprisedof two separate tables, identified by the subscripts a and b, one ofwhich converts an 8-bit byte into a 16-bit symbol having positive DSVand the other converting the same 8-bit byte into a 16-bit symbol havingnegative DSV.

The tables are categorized as follows: if the last bit of theimmediately preceding 16-bit symbol ends as a “1” or if the last twobits of that 16-bit symbol end as “10”, the next 16-bit symbol isselected from table T_(1a) or table T_(1b), depending upon whether it isdesirable that this next selected 16-bit symbol exhibit a positive DSV(thus calling for table T_(1a)) or a negative DSV (thus calling fortable T_(1b)).

If the immediately preceding 16-bit symbol ends with two, three or foursuccessive 0s, the next-following 16-bit symbol is selected from eithertable T₂ (that is, from either table T_(2a) or table T_(2b)) or fromtable T₃ (that is, from table T_(3a) or table T_(3b)).

If the immediately preceding 16-bit symbol ends with six, seven or eightsuccessive 0s, the next-following 16-bit symbol is selected from tableT₄.

The first 16-bit symbol that is generated immediately following a framesync pattern is selected from table T₁.

The 16-bit symbols produced from tables T₂ and T₃ differ from each otherin the following important respects: all 16-bit symbols read from tableT₂ include a “0” as the first bit and a “0” as the thirteenth bit.

All 16-bit symbols read from table T₃ include a “1” as the first orthirteenth bit or a “1” as both the first and thirteenth bit.

In the 8-to-16 conversion scheme used with the present invention, it ispossible that the very same 16-bit symbol may be generated in responseto two different 8-bit bytes. However, when the 16-bit symbolrepresentative of one of these bytes is produced, the next-following16-bit symbol is produced from table T₂; whereas when the 16-bit symbolrepresentative of the other byte is produced. the next-following 16-bitsymbol is produced from table T₃. It is appreciated that, by recognizingthe table from which the next-following 16-bit symbol is produced,discrimination between the two bytes which, nevertheless, are convertedinto the same 16-bit symbol may be readily achieved.

For example, let it be assumed that an 8-bit byte having the value 10and an 8-bit byte having the value 20 both are converted to the same16-bit symbol 0010000100100100 from table T₂. But, when this 16-bitsymbol represents the byte having the value 10, the next-following16-bit symbol is produced from table T₂, whereas when the aforenoted16-bit symbol represents the byte having the value 20, thenext-following 16-bit symbol is produced from table T₃. When the symbol0010000100100100 is demodulated, it cannot be determined immediately ifthis symbol represents the byte having the value 10 or the byte havingthe value 20. But, when the next-following 16-bit symbol is examined, itis concluded that the preceding symbol 0010000100100100 represents thebyte 10 if the next-following symbol is from table T₂, and representsthe byte having the value 20 if the next-following symbol is from tableT₃. To determine whether the next-following 16-bit symbol is from tableT₂ or table T₃, the demodulator merely needs to examine the first andthirteenth bits of the next-following symbol, as discussed above.

Table T_(a) (for example, table T_(1a)) includes 16-bit symbols having aDSV which increases in the positive direction. Conversely, the 16-bitsymbols which are stored in table T_(b) have a DSV which increases inthe negative direction. As an example, if the value of an 8-bit byte isless than 64, this byte is converted into a 16-bit symbol having arelatively large DSV. Conversely, if the value of the 8-bit byte is 64or more, this byte is converted into a 16-bit symbol having a small DSV.Those 16-bit symbols which are stored in table T_(a) have positive DSVand those 16-bit symbols which are stored in table T_(b) have negativeDSV. Thus, an input byte is converted into a 16-bit symbol havingpositive or negative DSV, depending upon which table is selected forconversion, and the value of the DSV is large or small,small, dependingupon the value of the input byte that is converted.

The tables T_(1a), T_(1b), . . . T_(4a), T_(4b) in FIG. 30 may beconstructed as ROMs 62–69. An input to be converted is supplied from aninput terminal 61 in common to each of these ROMs. The pair of tablesT_(a), T_(b) of a fundamental table are coupled to a selector switchwhich selects one or the other table to have read out therefrom the16-bit symbol which corresponds to the input byte read out therefrom. Asshown, selector switch 71 selectively couples the output from tableT_(1a) or table T_(1b) to an input x1 of an output switch 75. Similarly,switch 72 selectively couples table T_(2a) or table T_(2b) to an inputx2 of switch 75. Switch 73 selectively couples table T_(3a) or tableT_(3b) to input x3 of switch 75. Switch 74 selectively couples tableT_(4a) or table T_(4b) to input x4 of switch 75. Output switch 75selectively couples one of its inputs x1–x4 to an output terminal 78under the control of a table selector 76. Selector switches 71–74 selecteither table T_(a) or table T_(b) under the control of a DSV calculator77. The 16-bit symbol which ultimately is supplied to output 78 also iscoupled to the table selector and to the DSV calculator, as illustrated.

Table selector 76 senses the ending bits of the 16-bit symbol suppliedfrom switch 75 to output terminal 78 to determine whether fundamentaltable T₁, T₂, T₃ or T₄ should be selected, in accordance with the tableselecting conditions discussed above. It is appreciated that the tableselector thus controls switch 75 to select the 16-bit symbol read fromthe proper fundamental table. For example, if it is assumed that the16-bit symbol supplied to output terminal 78 ends with six, seven oreight successive 0s, switch 75 is controlled by the table selector tocouple its input x4 to the output terminal such that the next-following16-bit symbol is read from fundamental table T₄. DSV calculator 77calculates the accumulated DSV, which is updated in response to each16-bit symbol supplied to output terminal 78. If the DSV increases inthe positive direction, DSV calculator 77 controls selector switches71–74 to couple the outputs from their respective tables T_(b).Conversely, if the accumulated DSV is calculated to increase in thenegative direction, selector switches 71–74 are controlled by the DSVcalculator to couple the outputs from their respectively tables T_(a).It is expected, therefore, that if the preceding 16-bit symbol exhibitsa larger negative DSV, switches 71–74 are controlled to select the next16-bit symbol having a positive DSV; and the particular table from whichthis next 16-bit symbol is read is determined by table selector 76.Thus, the accumulated DSV is seen to approach and oscillate about 0.

An example of a 16-to-8 bit converter, that is, a demodulator compatiblewith the 8-to-16 bit modulator of FIG. 30, is illustrated in FIG. 31.Here, tables are used to carry out an inverse conversion from 16-bitsymbols to 8-bit bytes and such tables are identified as tables IT₁,IT₂, IT₃ and IT₄. These tables may be stored in ROMs 84, 85, 86 and 87.It is expected that each 8-bit byte read from a table corresponds to two16-bit symbols, one having positive DSV and the other exhibitingnegative DSV. Alternatively, if the 16-bit symbol is used as a readaddress, each 8-bit byte stored in a table may have two read addresses.Stated otherwise, each 8-bit byte may be stored in two separate readaddress locations.

An input terminal 81 is supplied with a 16-bit symbol, and this symbolis stored temporarily in a register 82 and then coupled in common toinverse conversion tables IT₁–IT₄. In addition, a table selector 83 iscoupled to input terminal 81 and to the output of register 82 so that itis supplied concurrently with the presently received 16-bit symbol andthe immediately preceding 16-bit symbol. Alternatively, table selector83 may be thought of as being supplied with the presently received16-bit symbol (from the output of register 82) and the next-following16-bit symbol. The table selector is coupled to an output selectorswitch 88 which couples to output terminal 89 either conversion tableIT₁ or conversion table IT₂ or conversion table IT₃ or conversion tableIT₄.

The manner in which table selector 83 operates now will be described. Asmentioned above, the first symbol that is produced immediately followingthe frame sync pattern is read from conversion table T₁ in FIG. 30.Table selector 83 thus operates to detect the frame sync pattern so asto control output switch 88 to couple table IT₁ to output terminal 89.

If, as mentioned above, a 16-bit symbol may represent one or the otherof two different 8-bit bytes, table selector 83 senses whether thenext-following 16-bit symbol, as supplied thereto from input terminal81, is from conversion table T₂ or conversion table T₃. Thisdetermination is made by examining the first and thirteenth bits of suchnext-following 16-bit symbol. If the table selector senses that thenext-following 16-bit symbol is from table T₂, output switch 88 issuitably controlled to select the inverse conversion table whichconverts the 16-bit symbol presently provided at the output of register82 to its proper 8-bit byte. A similar operation is carried out whentable selector 83 senses that the next-following 16-bit symbol had beenread from conversion table T₃ in FIG. 30.

The present invention converts an 8-bit byte into a 16-bit symbol,whereas the prior art converts an 8-bit byte into a 14-bit symbol andinserts three margin bits between successive symbols. Consequently,since the present invention uses only 16 bits in its bit stream ascompared to the prior art use of 17 bits, the modulation technique ofthe present invention results in an effective reduction in data of16/17, or about 6%.

While the present invention is particularly applicable to a CD-ROM onwhich computer data, video data, a combination of video and audio dataor computer files may be recorded, this invention is particularly usefulin recording and reproducing digital video discs (DVD) on which videodata and its associated audio data are recorded. Such data is compressedin accordance with the MPEG standard; and when compressed video data isrecorded on the disc, the subcode information included in each sectorheader (FIG. 10) includes a subcode address having the value 3 or thevalue 4 with the resultant subcode field appearing as shown in FIGS. 11Dor 11E. If the subcode address value is 3, the user data recorded in thesector conforms to the standard ISO 11172-2 (MPEG 1) or ISO 13818-2(MPEG 2). Data that is recorded in the subcode field, as shown in FIG.11D, represents the difference between the address of the sector whichcontains this subcode and the lead sector in which the previous Ipicture or next-following I picture is recorded. It is expected that anI picture (that is, an intraframe encoded picture, as mentionedpreviously) is recorded in two or more sectors. Of course, each sectorincludes a header. However, the distance data which is recorded in thesubcode field shown in FIG. 11D represents the distance to the lead, orfirst sector in which the previous I picture or next-following I pictureis recorded. If an I picture is recorded partially in one sector andpartially in another, the sector header of the “other” sector includes 0data to represent the previous I distance and the next I distance inFIG. 11D. That is, the previous I distance and the next I distance are0.

If the subcode address value is 4, the subcode field appears as shown inFIG. 11E and, as mentioned above, the picture type data indicateswhether the video data that is recorded in compressed form in thissector is I, P or B picture data and the temporal reference dataindicates the location in the sequence of pictures in which thisparticular video picture is disposed. The sector in which an I, P or Bpicture first is recorded is referred to as an I, P or B sector,respectively, even if such I, P or B picture data is recorded in atrailing portion of that sector, while other picture data is recorded ina leading portion thereof.

FIG. 32 is a block diagram of compression apparatus which is used tosupply to input terminal 121 of FIG. 1 MPEG compressed video data. Videoinformation, supplied as, for example, analog luminance (Y) and colordifference (R-Y and B-Y) signals are digitized by an analog-to-digitalconverter 101 and compressed in accordance with the MPEG compressionsystem by video compression circuitry 102. The compression system may beconsistent with the MPEG-1 standard (ISO 11172-2) or the MPEG-2 standard(ISO 13818-2). The compressed video data is stored in a buffer memory103 from which it is supplied to a multiplexor 107 for multiplexing withother data (soon to be described) which then is input to input terminal121 (FIG. 1). Information related to the compressed video data stored inbuffer memory 103 is supplied to system controller 110, this informationbeing indicative of, for example, whether the compressed video datacorresponds to an I, P or B picture, the temporal sequence of displaypictures in which this compressed video picture is located, time coderepresenting the time of receipt or time of recording of the video data,etc. The information derived from the stored, compressed video data andsupplied to the system controller is used to generate subcodeinformation that is recorded in the sector header. It is recalled fromFIG. 1 that this information is supplied from system controller 110 tosector header encoder 129 for insertion into the sector header of theuser data.

Audio signals, such as analog left-channel and right-channel signals Land R are digitized by an analog-to-digital converter 104 and compressedin an analog data compression circuit 105. This compression circuit mayoperate in accordance with the Adaptive Transform Acoustic Codingtechnique (known as ATRAC) consistent with MPEG-1 audio compression orMPEG-2 audio compression standards. It is appreciated that this ATRACtechnique presently is used to compress audio information in recordingthe medium known as the “Mini Disc” developed by Sony Corporation. Thecompressed audio data is supplied from compression circuit 105 to anaudio buffer memory 106 from which it subsequently is coupled to amultiplexor 107 for multiplexing with the compressed video data.Alternatively, compression circuit 105 can be omitted and the digitizedaudio data can be supplied directly to a buffer memory 106 as, forexample, a 16-bit PCM encoded signal. Selective information stored inthe audio buffer memory is coupled to the system controller for use ingenerating the subcode information that is recorded in the sectorheader.

Additional information, identified in FIG. 32 as sub-information,including character, computer, graphic and musical instrument fordigital interface data (MIDI) also is coupled to multiplexor 107.

Title data is generated by a character generator 111 which, for example,may be of conventional construction. The title data is identified asfill data and key data and is compressed by a compression circuit 112which encodes the title data in variable run length coding. Thecompressed title data is coupled multiplexor 107 for subsequentapplication to the input terminal 121 shown in FIG. 1.

Preferably, multiplexor 107 multiplexes the compressed video, audio andtitle data, together with the sub-information, in accordance with theMPEG-1 or MPEG-2 standard, as may be desired. The output of themultiplexor is coupled to input terminal 121 of FIG. 1 whereat themultiplexed data is ECC encoded, modulated and recorded on disc 100.

FIG. 33 is a block diagram of circuitry for recovering the video, audio,title and sub-information data that had been recorded on disc 100 andthat had been reproduced from the disc by the playback apparatus shownin FIG. 2. The input to the data recovery circuit shown In FIG. 33 isoutput terminal 224 of FIG. 2. This terminal is coupled to ademultlplexor 248 which demultiplexes the aforedescribed multiplexedvideo, audio and title data as well as the sub-information. Thedemultiplexor operates in accordance with the MPEG-1 or MPEG-2 standard,as may be desired, to separate the compressed video data, the compressedaudio data, the compressed tine data and the sub-information. Thecompressed video data is stored in a buffer memory 249 from which it isexpanded in expansion circuit 250, processed in a post processor 256,for example, as may be needed to conceal errors, and reconverted back toanalog form by digital-to-analog converter 251. Expansion circuit 250operates in accordance with the MPEG-1 or MPEG-2 standard such that theoriginal video information is recovered.

Post processor 256 also is adapted to superimpose graphical titleinformation on the recovered video data, as will be described below,such that the recovered title data may be suitably displayed, as bysuperposition on a video picture.

The separated audio data is supplied from demultiplexor 248 to an audiobuffer memory 252 from which it is expanded in an expansion circuit 253and reconverted to analog form by digital-to-analog convertor 254.Expansion circuit 253 operates in accordance with the MPEG-1 or MPEG-2or mini disc standard, as may be desired. If the audio data that isrecorded on disc 100 has not been compressed. expansion circuit 253 maybe omitted or bypassed.

As depicted in FIG. 33, the sub-information separated by demultiplexor248 is supplied as a direct output signal, consistent with therepresentation shown in FIG. 32 wherein such subinformation is notprocessed prior to being supplied to multiplexor 107 and no processingsubsequent to demultiplexor 248 is illustrated.

The separated title data is applied to title buffer memory 233 fromdemultiplexor 248 from which the title data is decoded by a titledecoder 260 that operates in a manner inverse to the operation ofcompression circuit 112 (FIG. 32). That is. decoder 260 may carry out aninverse variable length decoding operation. The decoded title data issupplied to post processor 256 for superposition onto the videoinformation that has been played back from the optical disc.

Demultiplexor 248 monitors the remaining capacities of buffer memories249, 252 and 233 to sense when these memories are relatively empty orfilled. The purpose of monitoring the remaining capacities of the buffermemories is to assure that data overflow therein does not occur.

System controller 230 and user interface 231 of FIG. 33 are the same assystem controller 230 and user interface 231 in FIG. 2.

While the present invention has been particularly shown and describedwith reference to preferred embodiments, it will be readily apparent tothose of ordinary skill in the art that various changes and variationsmay be made without departing from the spirit and scope of theinvention. To the extent that such variations and changes have beenmentioned herein, the appended claims are to be interpreted as includingsuch variations and changes as well as all equivalents to those featureswhich have been particularly disclosed.

1. A method of recording data on an optical disk having a diameter lessthan 140 mm, a thickness of 1.2 mm±0.1 mm and a recording area dividedinto a lead-in area, a program area and a lead-out area, said methodcomprising the steps of: providing user information for recording in aplurality of sectors in user tracks; providing table of contents (TOC)information for recording in a plurality of sectors in at least one TOCtrack, said TOC information including addresses of respective startsectors, each identifying a start sector of a respective user track;encoding both said user information and said TOC information in a longdistance error correction code having at least eight parity symbols;modulating the encoded user and TOC information; recording themodulated, encoded TOC information as embossed pits in said at least oneTOC track in said lead-in area; and recording the modulated, encodeduser information as embossed pits in said user tracks in said programarea with a track pitch in the range between 0.646 μm and 1.05 μm. 2.The method of claim 1 wherein each of said steps of recording isoperative to record said embossed pits with a linear density in therange between 0.237 μm per bit and 0.378 μm per bit.
 3. The method ofclaim 1 wherein the step of recording embossed pits in said program areais operative to record said program area in a portion of the disk havinga radius of from 20 mm to 65 mm.
 4. The method of claim 1 wherein saidstep of recording the modulated encoded TOC information includes thestep of recording is said program area modulated, encoded TOCinformation substantially identical to the TOC information recorded insaid lead-in area.
 5. The method of claim 1 wherein said step ofrecording said TOC information includes the steps of recording TOCidentification data for identifying a location of said at least one TOCtrack, recording a data configuration of said at least one TOC track,and recording a sector configuration of each of said plurality ofsectors.
 6. The method of claim 1 wherein said TOC information includesdata representative of disk size.
 7. The method of claim 1 wherein saidTOC information includes data representative of a time code associatedwith said user information.
 8. The method of claim 1 wherein said userinformation is reproducible at a selected one of plural playback speeds;and said step of recording said TOC information includes the step ofrecording data representative of said selected playback speed.
 9. Themethod of claim 1 wherein the step of encoding comprises encoding saiduser and TOC information in a convolution code.
 10. The method of claim1 wherein said TOC information is representative of record/playbackcharacteristics, diameter, recording capacity and number of recordtracks of said optical disk.
 11. The method of claim 10 wherein saidrecord/playback characteristics of said optical disk represent a readonly disk, a write once disk or an erasable disk.
 12. The method ofclaim 1 wherein said step of modulating comprises run length limited(RLL) modulating said encoded user and TOC information.
 13. The methodof claim 12 wherein said RLL modulating is (2,10) modulation, such thatsuccessive transitions are separated by no less than 2 data bit cellsand by no more than 10 data bit cells.
 14. The method of claim 13wherein said step of modulating further comprises converting n-bit datawords representing said user and TOC information to 2n-bit informationwords for recording.
 15. The method of claim 1 wherein said step ofencoding information in said long distance error correction code iscomprised of receiving input information data; inserting C2 and C1 holdsections at predetermined locations in said input data and therebyforming preliminary C1 words comprised of plural data symbols;generating C2 parity symbols in response to a predetermined number ofdata symbols of the same number of preliminary C1 words and replacing aC2 hold section in a preliminary C1 word with said C2 parity symbols toform a precursory C1 word, generating C1 parity symbols in response to aprecursory C1 word and inserting said C1 parity symbols into a C1 holdsection to form a C1 code word, and using a pre-established number ofsaid C1 code words as said long distance error correction encoded data16. The method of claim 15 wherein said step of recording comprisesrecording the symbols of the C1 code words in a symbol sequencedifferent from the symbol sequence of said preliminary C1 words.
 17. Themethod of claim 16 wherein a preliminary C1 code word is comprised ofodd and even symbols and wherein said step of recording records the oddsymbols together in an odd group and records the even symbols togetherin an even group.
 18. The method of claim 17 wherein each C1 code wordis formed of in symbols including m−n C1 parity symbols, where m and nare integers; and wherein:k=m×i+2×j−m, when j<m/2k=m×i+2×j−(m−1), when j≧m/2, where i is the sequential order of thepreliminary C1 words of input data, j is the sequential order of the msymbols in each preliminary C1 code word and k is the order in which them symbols are recorded on the disk.
 19. The method of claim 1 whereinsaid step of modulating comprises supplying said TOC and userinformation as n-bit bytes, reading from a selected one of pluralstorage tables a 2n-bit symbol in response to a supplied n-bit byte, andselecting said one storage table as a function of the preceding 2n-bitsymbol that had been read.
 20. The method of claim 19, whereinsuccessive 2n-bit symbols are run length limited.
 21. The method ofclaim 20 wherein different 2n-bit symbols are stored respectively in atleast two of said storage tables for the same n-bit byte.
 22. The methodof claim 21 wherein the 2n-bit symbols stored in one of said two storagetables exhibit positive digital sum value (DSV) and the 2n-bit symbolsstored in the other of said two storage tables exhibit negative DSV. 23.The method of claim 22 wherein the step of selecting said one storagetable is determined as a function of the number of “0” bits in which thepreceding 2n-bit symbol terminates and accumulated DSV of apredetermined number of preceding 2n-bit symbols.
 24. The method ofclaim 1 wherein each sector in at least said user tracks includes asector header at a leading portion thereof; and said step of recordinguser information includes recording in said sector header, a sector syncpattern, a sector address, an error detection code, and subcode data.25. The method of claim 24 wherein said subcode data in a given sectorincludes a subcode identifier and subcode information of a typeidentified by said subcode identifier.
 26. The method of claim 25wherein said subcode identifier is a subcode address.
 27. The method ofclaim 25 wherein said subcode information includes track identifyingdata which identifies the track in which said given sector is recorded,copyright data which indicates whether user information in said trackmay be copied, and application identifying data which identifies apredetermined application allotted to said user information in saidtrack.
 28. The method of claim 25 wherein said step of encoding saiduser information comprises compressing a predetermined display sequenceof picture data in accordance with selectively different types ofcompression-encoding technique, and said subcode information includestype identifying information for identifying the type ofcompression-encoding technique that is used to compress the datarecorded in said given sector and sequence information for identifyingthe location in said display sequence of the picture represented by thecompressed picture data that is recorded in said given sector.
 29. Themethod of claim 25 wherein said user information is variable over time,and said subcode information includes time code data representing timeinformation at which said user information is recorded.
 30. The methodof claim 25 wherein said user information is picture informationrepresenting a respective picture; and said step of recording comprisesrecording said picture information in at least one sector in said usertracks, and recording as subcode information first distance informationrepresenting the distance from said given sector to the sector in whichpicture information representing a next preceding picture is recordedand second distance information representing the distance from saidgiven sector to the sector in which picture information representing anext following picture is recorded.
 31. The method of claim 30 whereinsaid step of recording picture information comprises recording saidpicture information in a lead sector and at least one following sector.32. The method of claim 31 wherein said step of encoding said userinformation comprises compressing picture data to selectively formintraframe encoded picture data or predictively encoded picture data;and each of said first and second distance information represents thedistance from said given sector to the lead sector in which intraframeencoded picture data is recorded.
 33. Apparatus for recording data on anoptical disk having a diameter less than 140 mm, a thickness of 1.2mm±0.1 mm and a recording area divided into a lead-in area, a programarea and a lead-out area, said apparatus comprising: input means forproviding user information for recording in a plurality of sectors inuser tracks and table of contents (TOC) information for recording in aplurality of sectors in at least one TOC track, said TOC informationincluding addresses of respective start sectors, each identifying astart sector of a respective user track; encoding means for encodingboth said user information and said TOC information in a long distanceerror correction code having at least eight parity symbols; modulatormeans for modulating the encoded user and TOC information; and recordingmeans for recording the modulated, encoded TOC information as embossedpits in said at least one TOC track in said lead-in area and forrecording the modulated, encoded user information as embossed pits insaid user tracks in said program area with a track pitch in the rangebetween 0.646 μm and 1.05 μm.
 34. The apparatus of claim 33 wherein saidrecording means is operative to record said embossed pits with a lineardensity in the range between 0.237 μm per bit and 0.378 μm per bit. 35.The apparatus of claim 33 wherein said recording means is operative torecord said program area in a portion of the disk having a radius offrom 20 mm to 65 mm.
 36. The apparatus of claim 33 wherein saidrecording means is operative to record in said program area modulated,encoded TOC information substantially identical to the TOC informationrecorded in said lead-in area.
 37. The apparatus of claim 33 whereinsaid TOC information includes TOC identification data for identifying alocation of said at least one TOC track and configuration data foridentifying a data configuration of said at least one TOC track and asector configuration of each of said plurality of sectors.
 38. Theapparatus of claim 33 wherein said TOC information includes datarepresentative of disk size.
 39. The apparatus of claim 33 wherein saidTOC information includes data representative of a time code associatedwith said user information.
 40. The apparatus of claim 33 wherein saiduser information is reproducible at a selected one of plural playbackspeeds; and said TOC information includes data representative of saidselected playback speed.
 41. The apparatus of claim 33 wherein saidencoding comprises a convolution code encoder.
 42. The apparatus ofclaim 33 wherein said TOC information is representative ofrecord/playback characteristics, diameter, recording capacity and numberof record tracks of said optical disk.
 43. The apparatus of claim 42wherein said record/playback characteristics of said optical diskrepresent a read only disk, a write once disk or an erasable disk. 44.The apparatus of claim 33 wherein said modulator means is a run lengthlimited (RLL) modulator.
 45. The apparatus of claim 44 wherein said RLLmodulator performs (2,10) modulation. such that successive transitionsare separated by no less than 2 data bit cells and by no more than 10data bit cells.
 46. The apparatus of claim 45 wherein said modulatorincludes means for converting n-bit data words representing said userand TOC information to 2n-bit information words for recording.
 47. Theapparatus of claim 33 wherein said encoding means is comprised of meansfor receiving said user and TOC information as input data; means forinserting C2 and C1 hold sections at predetermined locations in saidinput data to thereby form preliminary C1 words comprised of plural datasymbols; means for generating C2 parity symbols in response to apredetermined number of data symbols of the same number of preliminaryC1 words; means for replacing a C2 hold section in a preliminary C1 wordwith said C2 parity symbols to form a precursory C1 word; means forgenerating C1 parity symbols in response to a precursory C1 word; andmeans for inserting said C1 parity symbols into a C1 hold section toform a C1 code word, with a pre-established number of said C1 code wordsconstituting said long distance error correction encoded data.
 48. Theapparatus of claim 47 wherein said recording means further includesmeans for recording the symbols of the C1 code words in a symbolsequence different from the symbol sequence of said preliminary C1words.
 49. The apparatus of claim 48 wherein a preliminary C1 code wordis comprised of odd and even symbols and wherein said means forrecording is operative to record the odd symbols together in an oddgroup and the even symbols together in an even group.
 50. The apparatusof claim 49 wherein each C1 code word is formed of in symbols includingm−n C1 parity symbols, where m and n are integers; and wherein:k=m×i+2×j−m, when j<m/2k=m×i+2×j−(m−1), when j≧m/2, where i is the sequential order of thepreliminary C1 words of input data, j is the sequential order of the msymbols in each preliminary C1 code word, and k is the order in whichthe m symbols are recorded on the disk.
 51. The apparatus of claim 33wherein said modulator means comprises an n-to-2n modulator in whichsaid TOC and user information are supplied as n-bit bytes, includingplural storage tables, each for storing 2n-bit symbols corresponding torespective n-bit bytes; means for reading from a selected one storagetable a 2n-bit symbol in response to a supplied n-bit byte; and meansfor selecting said storage table as a function of the preceding 2n-bitsymbol that had been read.
 52. The apparatus of claim 51, whereinsuccessive 2n-bit symbols are run length limited.
 53. The apparatus ofclaim 52 wherein at least two of said storage tables store different2n-bit symbols for the same n-bit byte.
 54. The apparatus of claim 53wherein the 2n-bit symbols stored in one of said two storage tablesexhibit positive digital sum value (DSV) and the 2n-bit symbols staredin the other of said two storage tables exhibit negative DSV.
 55. Theapparatus of claim 54 wherein said means for selecting said one storagetable includes means for sensing the number of “0” bits in which thepreceding 2n-bit symbol terminates, means for determining theaccumulated DSV of a predetermined number of preceding 2n-bit symbolsand means for selecting the storage table as a function of the sensednumber of “0” bits and the accumulated DSV.
 56. The apparatus of claim33 wherein each sector in at least said user tracks includes a sectorheader at a leading portion thereof; and said recording means isoperative to record in said sector header, a sector sync pattern, asector address, an error detection code, and subcode data.
 57. Theapparatus of claim 59 wherein said subcode identifier is a subcodeaddress.
 58. The apparatus of claim 59 wherein said subcode informationincludes track identifying data which identifies the track in which saidgiven sector is recorded, copyright data which indicates whether userinformation in said track may be copied, and application identifyingdata which identifies a predetermined application allotted to said userinformation in said track.
 59. The apparatus of claim 56 wherein saidsubcode data in a given sector includes a subcode identifier and subcodeinformation of a type identified by said subcode identifier.
 60. Theapparatus of claim 59 wherein said encoding means comprises means forcompressing a predetermined display sequence of picture data inaccordance with selectively different types of compression-encodingtechniques, and said subcode information includes type identifyinginformation for identifying the type of compression-encoding techniquethat is used to compress the data recorded in said given sector andsequence information for identifying the location in said displaysequence of the picture represented by the compressed picture data thatis recorded in said given sector.
 61. The apparatus of claim 59 whereinsaid user information is variable over time, and said subcodeinformation includes time code data representing time information atwhich said user information is recorded.
 62. The apparatus of claim 59wherein said user information is picture information representing arespective picture; and said recording means is operative to record saidpicture information in at least one sector in said user tracks, and torecord as subcode information first distance information representingthe distance from said given sector to the sector in which pictureinformation representing a next preceding picture is recorded and seconddistance information representing the distance from said given sector tothe sector in which picture information representing a next followingpicture is recorded.
 63. The apparatus of claim 62 wherein saidrecording means is further operative to record picture information in alead sector and at least one following sector.
 64. The apparatus ofclaim 63 wherein said encoding means includes means for compressingpicture data to selectively form intraframe encoded picture data orpredictively encoded picture data; and each of said first and seconddistance information represents the distance from said given sector tothe lead sector in which intraframe encoded picture data is recorded.65. A method of recording data on an optical disk having a diameter lessthan 140 mm and a recording area divided into a lead-in area, a programarea and a lead-out area, said method comprising the steps of: providinguser information for recording in a plurality of sectors in user tracks;providing table of contents (TOC) information for recording in aplurality of sectors in at least one TOC track, said TOC informationincluding addresses of respective start sectors, each identifying astart sector of a respective user track; encoding both said userinformation and said TOC information in a long distance error correctioncode having at least eight parity symbols; modulating the encoded userand TOC information; recording the modulated, encoded TOC information insaid at least one TOC track in said lead-in area; and recording themodulated, encoded user information in said user tracks in said programarea with a track pitch in the range between 0.646 μm and 1.05 μm. 66.Apparatus for recording data on an optical disk having a diameter lessthan 140 mm and a recording area divided into a lead-in area, a programarea and a lead-out area, said apparatus comprising: input means forproviding user information for recording in a plurality of sectors inuser tracks and table of contents (TOC) information for recording in aplurality of sectors in at least one TOC track, said TOC informationincluding addresses of respective start sectors, each identifying astart sector of a respective user track; encoding means for encodingboth said user information and said TOC information in a long distanceerror correction code having at least eight parity symbols; modulatormeans for modulating the encoded user and TOC information; and recordingmeans for recording the modulated, encoded TOC information in said atleast one TOC track in said lead-in area and for recording themodulated, encoded user information in said user tracks in said programarea with a track pitch in the range between 0.646 μm and 1.05 μm.
 67. Amethod of recording data on an optical disk having a diameter less than140 mm and a recording area divided into a lead-in area, a program areaand a lead-out area, said method comprising the steps of providing userinformation for recording in a plurality of sectors in user trackregions; providing table of contents (TOC) information for recording ina plurality of sectors in at least one TOC track, said TOC informationincluding addresses of respective start sectors, each identifying astart sector of a respective user track; encoding both said userinformation and said TOC information in a long distance error correctioncode having at least eight parity symbols; modulating the encoded userand TOC information; recording the modulated, encoded TOC information insaid at least one TOC track in said lead-in area; and recording themodulated, encoded user information in said user track regions in saidprogram area with a track pitch in the range between 0.646 μm and 1.05μm and with a linear density in the range between 0.237 μm per bit and0.387 μm per bit.
 68. Apparatus for recording data on an optical diskhaving a diameter less than 140 mm and a recording area divided into alead-in area, a program area and a lead-out area, said apparatuscomprising: input means for providing user information for recording ina plurality of sectors in user track regions and table of contents (TOC)information for recording in a plurality of sectors in at least one TOCtrack, said TOC information including addresses of respective startsectors, each identifying a start sector of a respective user track;encoding means for encoding both said user information and said TOCinformation in a long distance error correction code having at leasteight parity symbols; modular means for modulating the encoded user andTOC information; and recording means for recording the modulated,encoded TOC information in said at least one TOC track in said lead-inarea and the modulated, encoded user information in said user trackregions in said program area with a track pitch in the range between0.646 μm and 1.05 μm and with a linear density in the range between0.237 μm per bit and 0.387 μm per bit.
 69. A method of recording data onan optical disk having a diameter less than 140 mm and a recording areadivided into a lead-in area, a program area and a lead-out area, saidmethod comprising the steps of: providing user information for recordingin a plurality of sectors in user track regions; providing table ofcontents (TOC) information for recording in a plurality of sectors in atleast one TOC track, said TOC information including addresses ofrespective start sectors, each identifying a start sector of arespective user track; encoding both said user information and said TOCinformation in a long distance error correction code having at leasteight parity symbols; modulating the encoded user and TOC information;recording the modulated, encoded TOC information in said at least oneTOC track in said lead-in area; and recording the modulated, encodeduser information in said user track regions in said program area with atrack pitch in the range between 0.7 μm and 0.9 μm.
 70. Apparatus forrecording data on an optical disk having a diameter less than 140 mm anda recording area divided into a lead-in area, a program area and alead-out area, said apparatus comprising: input means for providing userinformation for recording in a plurality of sectors in user trackregions and table of contents (TOC) information for recording in aplurality of sectors in at least one TOC track, said TOC informationincluding addresses of respective start sectors, each identifying astart sector of a respective user track; encoding means for encodingboth said user information and said TOC information in a long distanceerror correction code having at least eight parity symbols; modularmeans for modulating the encoded user and TOC information; and recordingmeans for recording the modulated, encoded TOC information in said atleast one TOC track in said lead-in area and the modulated, encoded userinformation in said user track regions in said program area with a trackpitch in the range between 0.7 μm and 0.9 μm.
 71. A method of recordingdata on an optical disk having a diameter less than 140 mm and arecording area divided into a lead-in area, a program area and alead-out area, said method comprising the steps of: providing userinformation for recording in a plurality of sectors in user trackregions; providing table of contents (TOC) information for recording ina plurality of sectors in at least one TOC track, said TOC informationincluding addresses of respective start sectors, each identifying astart sector of a respective user track; encoding both said userinformation and said TOC information in a long distance error correctioncode having at least eight parity symbols; modulating the encoded userand TOC information; recording the modulated, encoded TOC information insaid at least one TOC track in said lead-in area; and recording themodulated, encoded user information in said user track regions in saidprogram area with a track pitch in the range between 0.646 μm and 1.05μm, wherein said optical disk has a linear velocity in the range of 3.3m to 5.3 m per second during a playback operation.
 72. Apparatus forrecording data on an optical disk having a diameter less than 140 mm anda recording area divided into a lead-in area, a program area and alead-out area, said apparatus comprising: input means for providing userinformation for recording in a plurality of sectors in user trackregions and table of contents (TOC) information for recording in aplurality of sectors in at least one TOC track, said TOC informationincluding addresses of respective start sectors, each identifying astart sector of a respective user track; encoding means for encodingboth said user information and said TOC information in a long distanceerror correction code having at least eight parity symbols; modularmeans for modulating the encoded user and TOC information; and recordingmeans for recording the modulated, encoded TOC information in said atleast one TOC track in said lead-in area and the modulated, encoded userinformation in said user track regions in said program area with a trackpitch in the range between 0.646 μm and 1.05 μm, wherein said opticaldisk has a linear velocity in the range of 3.3 m to 5.3 m per secondduring a playback operation.